CHAPTER IX
_DISINFECTION_
The object of modern bacteriology is not merely to accumulate tested facts of knowledge, nor only to learn the truth respecting the biology and life-history of bacteria. These are most important things from a scientific point of view. But they are also a means to an end; that end is the prevention of preventable diseases and the treatment of any departure from health. In a science not a quarter of a century old much has already been accomplished in this direction. The knowledge acquired of, and the secrets learned from, these tiny vegetable cells which have such potentiality for good or evil have been, in some degree, turned against them. When we know what favours their growth and vitality and virulence, we know something of the physical conditions which are inimical to their life; when we know how to grow them, we also know how to kill them.
We have previously made a cursory examination of the methods which are adopted for opposing bacteria and their products in the tissues and body fluids. We must now turn to consider shortly the modes which may be adopted in preventive medicine for opposing bacteria outside the body.
It will be clear at once that we may have varying degrees of opposition to bacteria. Some substances kill bacteria, and they are known as _germicides_; other substances prevent their development and resulting septic action, and these are termed _antiseptics_. The word _disinfectant_ is used more or less indiscriminately to cover both these terms. A _deodorant_ is, of course, a substance removing the odour of evil-smelling putrefactive processes. Here, then, we have the common designations of substances able to act injuriously on bacteria and their products outside, or upon the surface of, the body. But a moment's reflection will bring to our minds two facts not to be forgotten. In the first place, an antiseptic applied in very strong dose, or for an extended period, may act as a germicide; and, _vice versâ_, a germicide in too weak solution to act as such may perform only the function of an antiseptic. Moreover, the action of these disinfecting substances not only varies according to their own strength and mode of application, but it varies also according to the specific resistance of the protoplasm of the bacteria in question. Examples of the latter are abundant, and readers who have only assimilated the simple facts set forth in these pages are aware that between the bacillus of diphtheria and the spores of anthrax there is an enormous difference in power of resistance. In the second place, reflection will enable us to recall what has already been said, when discussing the requirements necessary for bacterial growth, respecting the physical conditions injurious to development. In a _cold temperature_, as a general rule, bacteria do not multiply with the same rapidity as at blood-heat. Within the limits of a _moist perimeter_ the air is, to all intents and purposes, germ-free. Direct _sunlight_ has a definitely germicidal effect in the course of time upon some of the most virulent bacteria we know. Here, then, are three examples of physical agents--low temperature, moist perimeter, sunlight--which, if strong enough in degree, or acting for a long enough period of time, become first antiseptics and then germicides. Yet for a limited period they have no injurious effect upon bacteria. These are simple points, and call for little comment, yet the pages of medical and sanitary journals reveal not a few keen controversies upon the injurious action of certain substances upon certain bacteria owing to the discrepancies, of necessity arising, between results of different skilled observers who have been carrying out different experiments with different solutions of the same substance upon different protoplasms of the same species of bacteria. We feel no doubt that in these pioneering researches much labour has been to some extent misspent, owing to the neglect of a common denominator. Only a more accurate knowledge of bacteria or a recognised standard for disinfecting experiments can ever supply such common denominator.
Species of bacteria for comparative observation-experiments upon the action of chemical or physical agents must be not only the same species, but cultured under the same conditions, and treated by the agent in the same manner, otherwise the results cannot be compared upon a common platform, or with any hope of arriving at exactly the same conclusions.
Sir George Buchanan laid down, in 1884, a very simple and suitable standard of what true disinfection meant, viz., the _destruction of the most stable known infective matter_. Such a test is high and difficult to attain unto; nevertheless, it is the only satisfactory one. Obviously many substances which are useful antiseptics in practical life would fall far short of such a standard, yet for true and complete disinfection such an ideal is the only adequate one.
Quite recently three or four workers at Leipzig[101] have drawn up simple directions, the adoption of which would considerably assist in securing a common standard for disinfectant research. They are as follows:
1. In all comparative observations it is imperative that _molecularly equivalent_ quantities of the reagents should be employed.
2. The bacteria serving as test objects should have equal power of resistance.
3. The numbers of bacteria used in comparative observation should be approximately equal.
4. The disinfecting solution must be always used at the same temperature in comparative experiments.
5. The bacteria must be brought into contact with the disinfectant with as little as possible of the nutrient material carried over. (This obviously will depend upon the object of the research.)
6. After having been exposed to the disinfectant for a fixed time, they should be freed from it as far as possible.
7. They should then be returned in equal numbers to the respective culture medium most favourable to the development of each, and kept at the same, preferably the optimum, temperature for their growth.
8. The number of surviving bacteria capable of giving rise to colonies in solid media must be estimated after the lapse of equal periods of time.
We may now turn from general principles to mention shortly some of the commoner methods and substances adopted to secure efficient disinfection. They are all divisible, according to Sir George Buchanan's standard, into two groups:
1. Heat in various forms;
2. Chemical bodies in various forms.
It should at the outset be understood that we desire in practical disinfection to inhibit or kill micro-organisms without injury to, or destruction of, the substance harbouring the germs for the time being. If this latter is of no moment, as in rags or carcasses, burning is the simplest and most thorough treatment. But with mattresses and beddings, bedclothes and garments, as well as with the human body, it is obvious that something short of burning is required.
1. From the earliest days of bacteriology heat has held a prominent place as a disinfector. But it is only in comparatively recent times that it has been fully established that _moist heat_ is the only really efficient form of heat disinfection. Boiling at atmospheric pressure (100° C.) is the oldest form of moist heat disinfection, and because of the simplicity of its application it has gained a large degree of popularity. But it must not be forgotten that mere boiling (100° C.) may not effectually remove the spores of all bacilli. Besides, boiling is not applicable to furniture, mattresses, and such-like frequently infected objects. For many of these _hot-air ovens_ were used in the early days. But it was found that such disinfection was no disinfection at all, for not only did it leave many organisms and spores untouched, but the degree of temperature was rarely, if ever, uniform throughout the substance being treated.
The failures following in the track of these methods were an indication of the need of some form of moist heat, viz., steam.
Here it will be necessary to digress for a moment into some of the characters of steam. When water is heated certain molecular changes take place, and at a certain temperature (100° C., 212° F.) the water becomes steam, or _vapour_, and on very little cooling will condense. But if the vapour is heated, it will become practically a gas, and will not condense until it has lost the whole of the heat, _i. e._, the heat of making water into vapour plus the heat of making vapour into gas. A gas proper is, then, the vapour of a liquid of which the boiling-point is substantially below its actual temperature. But we know that the temperature at which it boils depends upon the pressure to which it is subjected (Regnault's law). Hence in reality "steam at any temperature whatever may be a vapour proper, provided the pressure is such as prevents the liquid from boiling below that temperature." In such a condition of vapour it is termed _saturated steam_. But if it is at that same pressure further heated, it becomes practically a gas, and is called _superheated steam_. The former can condense without cooling; the latter cannot so condense at the same pressure. Saturated steam condenses immediately it meets the object to be disinfected, and gives out its latent heat; superheated steam acts by conduction, and not uniformly throughout the object. Its advantage is that it dries moistened objects. As a disinfecting power, superheated steam is much less than saturated steam. There is one further term which must be defined, namely, _current steam_. This is steam escaping from a disinfector as fast as it is admitted, and may be at atmospheric or higher temperatures. The disinfecting temperature which is now used as a standard is _an exposure to saturated steam of 115° C. for fifteen minutes_.
A number of different kinds of apparatus have been invented to facilitate disinfection to this standard on a large scale. Most sanitary authorities of importance are now supplied with some form of steam disinfector, though many are unable to go to the expense of high-pressure disinfectors. Professor Delépine has pointed out[102] that a current of steam at low pressure may completely disinfect. Whilst such simple current-steam machines have thus been demonstrated as efficient bactericides, for all practical purposes it is important to have disinfectors capable of giving temperatures considerably above 100° C., of simple construction, having steam power of uniform temperature and rapid penetration, and containing, when in action, a minimum of superheated steam. In addition to these characters of a first-rate steam disinfector, two other important points should be borne in mind, namely, the air must be completely ejected from the disinfection chamber before the results due to steam are obtained, and some sort of automatic index giving a record of each disinfection is indispensable.
We may turn from these general principles to mention shortly some of the types of steam disinfectors most commonly in use. They are four, namely, the Washington Lyon, the Equifex (Defries), the Thresh, and the Reck.
_Washington Lyon's_ apparatus consists of an elongated boiler having double walls, with a door at each end. The body of the apparatus is jacketed. The whole is large enough to admit of bedding and mattresses, and generally is so arranged that one end opens into one room, and the other end opens into another room. This convenient position admits of inserting infected articles from one room and receiving them disinfected into the other room. Possible reinfection is thereby prevented. Steam is admitted into the jacket at a pressure of between twenty and twenty-five pounds, and is generally twenty pounds in the interior of the cylinder. At the end of the operation a partial vacuum is created, by which means much of the moisture on the articles may be removed. In some cases a current of warm air is admitted before disinfection in order to diminish the extent of condensation.
The _Equifex_ (Defries) contains no steam jacket, but coils of pipes are placed at the top and bottom of the apparatus, with the object of imparting to the steam as much heat as is lost by radiation through the walls of the disinfecting chamber, and at the same time of preventing undue condensation. The air is first removed by a preliminary current of steam, after which steam at a pressure of ten pounds is intermittently introduced and allowed to escape. The object of this proceeding is to remove air from the pores of the articles to be disinfected by the sudden expansion of the film of water previously condensed on their surface. The apparatus introduced by _Dr. Thresh_ was constructed with a view of overcoming the objection to some of the other machines that bulky articles retained a large percentage of moisture, thus necessitating the use of some additional drying apparatus. A central chamber receives the articles to be disinfected, and is surrounded by a boiler containing a solution of calcium chloride at a temperature of 225° F. This is heated by a small furnace, and the steam given off (218-300° F.) is conducted into the central chamber. The steam is not confined under any pressure except that of the atmosphere. When the steam has passed for a sufficient length of time, it is readily diverted into the open air. Hot air is now introduced, and at the expiration of an hour the articles may be taken out disinfected and as dry as they were when inserted. The apparatus is comparatively inexpensive, and not of a complicated nature. The current steam is saturated, and at a temperature a few degrees above the boiling-point. Many experiments have been performed with this apparatus, and there is now a large amount of evidence in favour of it and current steam disinfection.
_Reck's_ apparatus is another kind of saturated steam disinfector, which resembles the Equifex, but differs from it in employing steam as a current.
It is probable that many other forms of steam disinfector will be invented, and each will have its enthusiastic supporters. Even at the time of writing some excellent results are announced from America.
2. The effects of _chemical substances_ as solutions, or in spray form, upon bacteria have been observed from the earliest days of bacteriology. To some decomposing matter or solution a disinfectant was added and sub-cultures made. If bacteria continued to develop, the disinfection had not been efficient; if, on the other hand, the sub-culture remained sterile, disinfection had been complete. From such rough-and-ready methods large deductions were drawn, and it is hardly too much to say that no branch of bacteriology contains such a vast mass of unassimilated and unassimilable statements as that relating to research into disinfectants. Most of the tabulated and recorded results are conspicuous in having no standard as regards bacterial growth. Yet without such a standard results are not comparable.
Silk threads, impregnated with anthrax spores, were placed in bottles containing carbolic acid of various strengths, and at stated periods threads were removed and placed in nutrient media, and development or otherwise observed. But, as Professor Crookshank[103] has pointed out, this method is fallacious, the thread being still wet with the solution when transferred to the medium, and thus modified in culture, possibly even inhibited altogether. It is unnecessary for us here to discuss every mode adopted by investigators in similar researches. We may just mention that the most approved methods at the present time are based upon two simple plans of exposure. In one we use a known volume of recent broth culture of an organism grown under specified conditions. To this is added a measured quantity of the antiseptic. At stated periods loopfuls of the broth and antiseptic mixture are sub-cultured in fresh-sterilised broth, and resulting development or otherwise closely observed. The other method is practicable when we are dealing with volatile bodies. In such cases a standard culture is made of the organism in broth at a standard temperature. Into this are dipped small strips of sterilised linen. When thoroughly impregnated these are removed from the broth and subsequently dried over sulphuric acid in a vacuum at 38° C. These may now be exposed for a longer or shorter period to the fumes of the antiseptic in question, and broth cultures made at the end of the exposure. It is obvious that a very large number of modifications are possible of these two simple devices for testing the bactericidal power of chemical substances. It should be remembered that here, perhaps, more than anywhere else in bacteriological research, careful control experiments are absolutely necessary.
_Mineral acids_ (nitric, hydrochloric, sulphuric), especially concentrated, are all germicides.
The _halogens_--chlorine, bromine, iodine, and fluorine--are, all four, disinfectants, but not used in practice. They are named in their order of power as such.
A number of separate bodies, such as _chloroform_ and _iodoform_, have been much advocated as antiseptics. The cost of the former and odour of the latter have, however, greatly militated against their general adoption.
_Chloride of lime_ is a powerful disinfectant. Professor Sheridan Delépine and Dr. Arthur Ransome have demonstrated its germicidal effect as a solution applied directly to the walls of rooms inhabited by tuberculous patients.[104] It may also be used in solid form for dusting decomposing matter.
_Mercuric chloride_ (corrosive sublimate) has been an accepted germicide for some time. But the experiments of Behring, Crookshank, and others have proved that the weaker solutions cannot be relied upon. This is, in part, due to the fact that it forms in albuminous liquids an albuminate of mercury which is inactive. Dilute solutions have the further disadvantage of being unstable. Various authorities recommend a solution of 1-500 as a germicide, and much weaker solutions are, of course, antiseptic. An ounce each of corrosive sublimate and hydrochloric acid in three gallons of water makes an efficient disinfectant.
_Potassium permanganate_ is, of course, the chief substance in Condy's fluid, as _zinc chloride_ is in Burnett's disinfecting fluid. A 5 per cent. of the former and a 2-1/2 per cent. of the latter are germicidal.
_Boracic acid_ is one of the most useful antiseptics with which to wash sore eyes, or preserve tinned foods or milk. It is not a strong germicide, but an unirritating and effective wash. Many cases of its addition to milk have found their way into the law courts, owing to cumulative poisoning, and it should only be used with the very greatest care as a food preservative.
_Carbolic acid_ has come into prominence as an antiseptic since its adoption by Lister in antiseptic surgery. It is cheap, volatile, and effective. One part in 400 is antiseptic, and 1 in 20 germicidal. As a wash for the hands the former is used, and a weaker solution for the body generally. Carbolic soap and similar toilet combinations are now very common. At one time it appeared as if corrosive sublimate would oust carbolic from the first place as an antiseptic solution, but a large number of experiments have confirmed opinion in favour of carbolic. Professor Crookshank found that carbolic acid, 1 in 40, acting for only one minute is sufficient to destroy _Streptococcus pyogenes_, _S. erysipelatis_, and _Staphylococcus pyogenes aureus_, and in the strength of 1 in 20 carbolic acid completely sterilised tubercular sputum when shaken up with it for one minute.
_Creosol_, a member of the phenol series, is a good disinfectant, and the active element in lysol, Jeye's fluid, creoline, izal, and creosote.
_Sulphurous acid_ is one of the commonest disinfectants employed for fumigation--the old orthodox method of disinfecting a room in which a case of infective disease has been nursed. It is evolved, of course, by burning sulphur. For each thousand cubic feet from one to five pounds of sulphur is used, and the walls may be washed with carbolic acid. Dr. Kenwood carried out some experiments in 1896[105] which appear to support the disinfecting power of sulphur fumes. He found that the _Bacillus diphtheriæ_ was not killed, though markedly inhibited, when the sulphurous gas (SO_{2}) did not much exceed .25 per cent. But the bacillus was killed where the sulphur fumes exceeded .5 per cent. Both these results had reference to the SO_{2} in the air in the centre of the room at a height of four feet, and after the lapse of four hours. There can be little doubt that fuming a sealed-up room with sulphur fumes in a moist atmosphere, and leaving it thus for twenty-four hours, is generally, if not always, efficient disinfection. It will kill the bacillus of diphtheria, though not always more resistant germs. Moreover, its simplicity of adoption is greatly in its favour. Anyone can readily apply it by purchasing a few pounds weight of ordinary roll sulphur and burning this in a saucer in the middle of a room which has had all its crevices and cracks in windows and walls blocked up with pasted paper. _Nitrous fumes_ may also be used in this way.
Recently _formalin_ has come much in favour as a room disinfectant. Formalin is a 40 per cent. solution of formaldehyde in water, a gas discovered by Hofmann in 1869. This gas is a product of imperfect oxidation of methyl alcohol, and may be obtained by passing vapour of methyl alcohol, mixed with air, over a glowing platinum wire or other heated metals, such as copper and silver. It is the simplest of a series of aldehydes, the highest of which is palmitic aldehyde. Its formula is CH_{2}O, and it is a colourless gas with a pungent odour, and having penetrating and irritating properties, particularly affecting the nasal mucous membrane and the eyes of those working with it. It is readily soluble in water, and in the air oxidises into formic acid (CH_{2}O_{2}). This latter substance occurs in the stings of bees, wasps, nettles, and various poisonous animal secretions. Formalin is a strong bactericide even in dilute solutions, and, of course, volatile. A solution of 1 to 10,000 is said to be able to destroy the bacilli of typhoid, cholera, and anthrax. A teaspoonful to ten gallons of milk is said to retard souring. When formalin is evaporated down, a white residue is left known as paraform. In lozenge form this latter body is used by combustion of methylated spirit to produce the gas. Hence we have three common forms of the same thing--_formalin_, _formic aldehyde_, _paraform_--each of which yields _formic acid_, and thus disinfects. The vapour cannot in practice be generated from the formalin as readily as from the paraform.
By a variety of ingenious arrangements formic aldehyde has been tested by a large number of observers during the last two or three years. We may refer to three modes of application. 1. _The sprayer_ (Equifex apparatus) produces a mixture of air and solution for spraying walls, ceilings, floors, and sometimes garments. 2. _The autoclave_ (Trillat's apparatus). In this a mixture of a 30-40 per cent. watery solution of formaldehyde and calcium chloride (4-5 per cent.) is heated under a pressure of three or four atmospheres, and the almost pure, dry gas is conducted through a tube passing through the keyhole of the door into the sealed-up room. 3. _The paraform lamp_ (the Alformant). The principle of this lamp is that the hot, moist products from the combustion of methylated spirit act upon the paraform tablets, converting them into gas. Most of the conclusions derived from experiments with these three different forms of apparatus are the same. It is agreed that the gas is harmless to colours and metal and polished wood. The vapour acts best in a warm atmosphere. As for its action on bacteria, it compares favourably with any other disinfectant. In 1 per cent. solution formalin destroys non-spore-bearing bacteria in thirty to sixty minutes.
Many observers have decried formaldehyde on account of its professed lack of penetrating power. Professor Delépine, however, states[106] that it possesses "penetration powers probably greater than those of most other active gaseous disinfectants. _Bacillus coli_, _B. tuberculosis_, _B. pyocyaneus_, and _Staph. pyogenes aureus_ were killed in dry or moist state, even when protected by three layers of filter paper." In Professor Delépine's opinion, the vapours of phenol, izal, dry chlorine, and sulphurous acid have, under the same conditions, given inferior results.
We may now shortly summarise the foregoing facts respecting antiseptics and disinfection in the simplest terms possible to afford facility to the uninitiated in practical application:
_To disinfect a room_, seal up cracks and crevices, and burn at least one pound of roll sulphur for every 1,000 cubic feet of space.[107] Many authorities recommend four or five pounds of sulphur to the same space. Let the room remain sealed up for twenty-four hours.
_To disinfect walls_, wash with chloride of lime solution (1-100) or carbolic acid (1-40). This latter solution may be used to wipe down furniture. Either or both may be used _after_ sulphur fuming. Formic aldehyde may also be used by lamp or autoclave.
_To disinfect bedding_, _etc._, the steam sterilisation secured in a Thresh, Equifex, or Lyon apparatus is the best. Rags and infected clothing, unless valuable, should be burnt.
_To disinfect garments and wearing apparel_, they should be washed in a disinfectant solution, or fumed with formic aldehyde.
_To disinfect excreta or putrefying solutions_, enough disinfectant should be added to produce _in the solution or matter being disinfected_ the percentage of disinfectant necessary to act as such. Adding a small quantity of antiseptic to a large volume of fluid or solid is as useless as pouring a small quantity of antiseptic down a sewer with the idea that such treatment will disinfect the sewage. The mixture of the disinfectant with the matter to be disinfected must contain the standard percentage for disinfection. Chloride of lime is a common substance for use in this way. Potassium permanganate (1-100) and carbolic (1-100), and many manufactured bodies containing them, are also widely used. Drs. Hill and Abram recommend[108] that the excreta and disinfectant be thoroughly mixed and stand for at least half an hour. For various reasons they particularly advise _chinosol_ as the most convenient disinfectant for this specific purpose.
_Antiseptics for wounds._ Carbolic acid (1-40) or corrosive sublimate (1-1,000) are commonly used in surgical practice. Boracic acid is one of the most unirritating antiseptics which are known. It may be used in saturated watery solution (1-30) or dusted on copiously as fine powder. It is especially applicable in open wounds, and as an eye-wash.
_To disinfect hands and arms._ Operating surgeons are those to whom it is a most urgent necessity to cleanse hands and arms antiseptically. Carbolic acid (1-20, or 1-40) is used for this purpose.
It is hardly necessary to add that in a case of infectious disease occurring in a household many of these modes of application, perhaps all of them, must be adopted. Formalin is probably the best gaseous disinfectant which we have, but its use does not, and should not, preclude the simultaneous adoption of other methods.
APPENDIX
It is proposed to add one or two notes on certain technical points in bacteriological work, with a view to assisting those medical men not able to obtain the advantages of a well-equipped laboratory, and yet desirous of occasionally attempting some practical bacteriology.
1. _General Examination._ All fluids may be examined for bacteria in two chief ways:
(_a_) A small quantity may be placed on a cover-glass or slide, dried over a lamp or bunsen flame, and stained with aniline dyes for a few minutes. It is then ready for microscopic examination. It is obvious that the result will generally be a _mixture_ of bacteria, for which differentiating stains may be used (Gram, Ziehl-Neelsen, etc.).
(_b_) A minute drop of the suspected fluid may be added to various fluid media (broth, liquefied gelatine, etc.) and then plated out upon small sterilised sheets of glass. In the course of two or three days the contained bacteria will reveal themselves in characteristic colonies, which may be examined, and if possible sub-cultured, and carefully studied.
_Double-Staining Methods._ These are various, and are used when it is desired to stain the bacteria themselves one colour, and the matrix or ground substance in which they are situated another colour. Three of the commoner methods are those of Ehrlich, Neelsen, and Gram. They are as follows:
_Ehrlich's Method._ "Five parts of aniline oil are shaken up with 100 parts distilled water, and the emulsion filtered through moistened filter paper. A saturated alcoholic solution of fuchsine, methyl-violet, or gentian-violet is added to the filtrate in a watch-glass, drop by drop, until precipitation commences. Cover-glass preparations are floated in this mixture for fifteen to thirty minutes, then washed for a few seconds in dilute nitric acid (one part nitric acid to two of water), and then rinsed in distilled water. The stain is removed from everything except the bacilli; but the ground substance can be after-stained brown if the bacilli are violet, or blue if they have been stained red" (Crookshank, _Bacteriology and Infective Diseases_, p. 89).
_Gram's Method._ The primary stain in this method is a solution of aniline gentian-violet (saturated alcoholic solution of gentian-violet 30 cc., aniline water 100 cc.), which stains both ground substance and bacteria in purple. The preparation is next immersed in the following solution for half a minute or a little more:
Iodine 1 part Potassium iodide 2 parts Distilled water 300 parts
In this short space of time the iodine solution acts as a mordant of the purple colour in the bacteria, but not in the ground substance. Hence, if the preparation be now (when it has assumed a _brown_ colour) washed in alcohol (methylated spirit), the ground substance slowly loses its colour and becomes clear. But the bacteria retain their colour, and thus stand out in a well-defined manner. Cover-glass preparations decolourise more quickly than sections of hardened tissue, and they should only be left in the methylated spirit until no more colour comes away. The preparation may now be washed in water, dried, and mounted for microscopic examination, or it may be double-stained, that is, immersed in some contrast colour which will lightly stain the ground substance. Eosin or Bismarck brown are commonly used for this purpose. The former is applied for a minute or two, the latter for five minutes, after which the specimen is passed through methylated spirit (and preferably xylol also) and mounted. The result is that the bacteria appear in a dark purple colour on a background of faint pink or brown. Carbol-thionine blue, picro-carmine, and other stains are occasionally used in place of the aniline gentian-violet, and there are other slight modifications of the method.
_Ziehl-Neelsen Method._ Here the primary stain is a solution of carbol-fuchsin:
Fuchsin 1 part Absolute alcohol 10 parts 5 per cent. aqueous solution of carbolic acid 100 parts
It is best to heat the dye in a sand-bath, in order to distribute the heat evenly. The various stages in the staining process are as follows: (_a_) The cover-glass with the dried film upon it is immersed in the hot stain for one to three minutes. (_b_) Remove the cover-glass from the carbol-fuchsin, and place it in a capsule containing a 25 per cent. solution of sulphuric acid to decolourise it. Here its redness is changed into a slate-grey colour. (_c_) Wash in water, and alternately in the acid and water, until it is of a faint pink colour. (_d_) Now place the cover-glass for a minute or two in a saturated aqueous solution of methylene-blue, which will counter-stain the decolourised ground substance blue. (_e_) Wash in water. (_f_) Dehydrate by rinsing in methylated spirit, dry, and mount. A pure culture of bacteria will not necessarily require the counter-stain (methylene-blue). Sections of tissue may require twenty to thirty minutes in the primary stain (carbol-fuchsin). This stain is used for tubercle and leprosy. With a little practice the staining of the bacillus of tubercle when present in pus or sputum becomes a very simple and accurate method of diagnosis. A small particle of sputum or pus is placed between two clean cover-glasses and thus pressed between the thumb and finger into a thin film. This is readily dried and stained as above, the bacillus of tubercle appearing as a delicately-beaded red rod with a background of blue.
_Bacteriological Diagnosis._ The following points must be ascertained in order to identify any particular micro-organism:
(1) Its morphology, bacillus, coccus, spirillum, etc.; the presence or absence of involution forms.
(2) Motility by the unstained cover-glass preparation ("hanging drop"); note presence of flagella.
(3) Presence of spores, their appearance and position.
(4) Whether or not the organism stains with Gram's method.
(5) The character of the growth upon various media (gelatine, agar, milk, potato, broth); the presence or absence of liquefaction in the gelatine culture; its power of producing acid, gas, or indol.
(6) Whether it is aërobic or anaërobic.
(7) Its colour in cultivation.
(8) If it is a disease-producing organism under examination, its effect upon the animal tissues and the course of the disease should be observed.
There are other points of importance, but the above are essential to a right conclusion.
_Diagnosis in Special Diseases:_
(1) _Diphtheria._ This disease may be bacteriologically diagnosed with a minimum of apparatus and equipment. By means of a swab a rubbing from a suspected throat is readily obtained. This may be examined by the microscope, or sub-cultured on favourable medium. Blood serum is perhaps the best, but, as Hewlett remarks, "If no serum tubes can be had, an egg may be used. It is boiled hard, the shell chipped away from one end with a knife sterilised by heating, and the inoculation made on the exposed white surface; the egg is then placed, inoculated end down, in a wine-glass of such a size that it rests on the rim and does not touch the bottom. A few drops of water may with advantage be put at the bottom of the glass to keep the egg-white moist. The preparation is kept in a warm place for twenty-four to forty-eight hours and then examined." The examination, of course, consists in staining and preparing for the microscope and observing the form, arrangement, and characters of the organism or organisms present. A small piece of the membrane may be detached, washed in water, and stained for the bacilli.
(2) _Tubercle_ (Ziehl-Neelsen's stain, _vide supra_).
(3) _Typhoid_ (_Enteric Fever_).
_Widal's Reaction._ This diagnostic test depends upon the effect which the blood of a person suffering from typhoid fever has upon the _Bacillus typhosus_. The effect is twofold. In the first place, the actively motile _B. typhosus_ becomes immotile; and secondly, there is an agglutination, or grouping together in colonies, of the _B. typhosus_. Neither of these features occurs if healthy human blood is brought into contact with a culture of the typhoid bacillus. There are various ways in which this "serum diagnosis" can be carried out. The simplest and quickest method is as follows: To ten drops of a twenty-four or forty-eight-hours-old neutral broth culture of the typhoid bacillus one drop of the blood serum to be tested is added. The serum and culture are rapidly mixed in the trough of a hollow ground slide (such as is used for the "hanging drop"), and a single drop is taken, placed upon an ordinary clean slide, and a cover-glass superimposed. The positive reaction of agglutination and immotility, if the blood comes from a case of typhoid fever, will probably appear within fifteen or twenty minutes. The fluid culture of typhoid may be taken from an agar culture as well as from broth. In both cases it may be desirable to filter through ordinary filter paper to remove any normally agglutinated masses of bacilli before commencing the test.
In his first experiments Widal used a test-tube in the following manner: The blood to be tested is diluted by one part of it being added to fifteen parts of broth in a test-tube. The mixture is inoculated with a drop of a typical _Bacillus typhosus_ culture. The tube is then incubated at 37° C. for twenty-four hours, after which it is examined. If the reaction be positive, the broth appears comparatively clear, but at the bottom of the test-tube a more or less abundant sediment will be found. This is due to the clumps of bacilli having fallen owing to gravity. If, on the other hand, the reaction is negative, the broth will appear more or less uniformly turbid.
For the _apparatus_ required to carry out the simpler methods of bacteriological work reference should be made to the standard laboratory text-books, which furnish all necessary details. A good microscope, with a 1/12 oil immersion lens, is, of course, essential. This can now be obtained for about £16 (Beck, Swift, Baker, Watson, etc.), and the other necessary apparatus is readily obtainable of Baird and Tatlock, Hatton Garden, E. C., and other makers.
FOOTNOTES:
[1] _The Contemporary Review_, November, 1897, p. 719.
[2] Some notable exceptions are found in the work of the Bath and West of England Society, Lord Vernon's model dairy, and the Essex County Council Bacteriological Teaching Laboratory.
[3] We propose throughout to use the term _bacterium_ (pl. _bacteria_) in its generic meaning, unless especially stated to the contrary. It will also be synonymous with the terms _microbe_, _germ_, and _micro-organism_. The term _bacillus_ will, of course, be restricted to a rod-shaped bacterium.
[4] Migula has recently (1896) suggested that the Schizomycetes should be subdivided into _Coccaceæ_, _Bacteriaceæ_, _Spirillaceæ_ (spirilla, spirochæta), _Chlamydobacteriaceæ_ (Streptothrix, Crenothrix, Cladothrix), and _Beggiatoa_.
[5] A one-twelfth oil immersion lens is requisite for the study of the lower bacteria.
[6] A _flagellum_ is a hair-like process arising from the poles or sides of the bacillus. It must not be confused with a _filament_, which is a thread-like growth of the bacillus itself.
[7] A "pure culture" is a growth in an artificial medium outside the body of one species of micro-organism only.
[8] Some pathogenic germs (suppuration and typhoid) can withstand freezing for weeks.
[9] G. J. Romanes, _Darwin and After Darwin_, vol. ii., 231.
[10] It will be observed that there is a marked difference between the effects of dry heat and moist heat. Moist heat is able to kill organisms much more readily than dry, owing to its penetrating effect on the capsule of the bacillus. Dry heat at 140° C. (284° F.), maintained for three hours, is necessary to kill the resistant spores of _Bacillus anthracis_ and _B. subtilis_, but moist heat at fifty degrees less will have the same effect. It is from data such as these that in laboratories and in disinfecting apparatus moist heat is invariably preferred to dry heat. For with the latter such high temperatures would be required that they would damage the articles being disinfected. Koch states the following figures for general guidance: Dry heat at a temperature of 120° C. (248° F.) will destroy spores of mould fungi, micrococci, and bacilli in the absence of their spores; for the spores of bacilli 140° C. (284° F.), maintained for three hours, is necessary; moist heat at 100° C. (212° F.) for fifteen minutes will kill bacilli and their spores.
[11] Water from a house cistern is rarely a fair sample. It should be taken from the main. If taken from a stream or still water, the collecting bottle should be held about a foot below the surface before the stopper is removed.
[12] The _cubic centimetre_ (cc.) is a convenient standard of fluid measurement constantly recurring in bacteriology. It is equal to 16-20 drops, and 28 cc. equal one fluid ounce.
[13] The gelatine is reduced to liquid form by heating in a water-bath. Before inserting the suspected water it is essential that the gelatine be under 40° C, or thereabouts, in order not to approach the thermal death-point of any bacteria.
[14] _Micro-organisms in Water_ (1894).
[15] Report on the Micro-organisms of Sewage, Reports to L. C. C., 1894, No. 216.
[16] Harben Lectures, 1896.
[17] Report on the Metropolitan Water Supply.
[18] The methods adopted for making a quantitative and qualitative examination of sewage are precisely analogous to those used in milk research. Dilution with sterilised water previous to plating out on gelatine in Petri dishes is essential (1 cc. to 10,000 cc. of sterile water, or some equally considerable dilution), otherwise the large numbers of germs would rapidly liquefy and destroy the film. Special methods must be used for the isolation of special organisms; phenol-gelatine, Elsner medium, indol reaction, "shake" cultures, Parietti broth, etc., must often be resorted to for special bacteria. Spores of bacteria may always be numerically estimated by adding the suspected water or sewage to gelatine, and then heating to 80° C. for ten minutes before plating out. This temperature removes the bacilli, but leaves the spores untouched.
[19] The bacilli of typhoid can live in crude sewage (Klein), but only for a very short period. When sewage is diluted with large quantities of water the case is very different. _Bacillus coli_ flourishes in sewage.
[20] Annual Report of the Medical Officer of the Local Government Board, 1897-98, p. 210.
[21] John Tyndall, F.R.S., _Floating Matter of the Air_.
[22] Flügge has lately attempted to demonstrate that an air current having a velocity of four metres per second can remove bacteria from surfaces of liquids by detaching drops of the liquid itself.
[23] Hewlett and Thomson graphically demonstrated the bactericidal power of the nasal mucous membrane by noting the early removal of _Bacillus prodigiosus_, which had been purposely placed on the healthy Schneiderian membrane of the nose.
[24] _Pathological Society of London, Transactions_, 1897.
[25] _Annali d'Igiene Sperimentale_, vol. v. (1895), fasc. 4.
[26] _Public Health_, vol. x., No. 4, p. 130 (1898).
[27] Flügge, _Grundriss der Hygiene_, 1897.
[28] _Zeitschrift für Hygiene_, vols. xxiv.-xxvi.
[29] _Annales de Micrographie._
[30] E. A. Schäfer, F.R.S., _Text-book on Physiology_, vol. i., p. 312.
[31] The unorganised ferments are frequently otherwise classified than as above, not according to the locality, but according to the function. The chief are these:--_amylolytic_, those which change starch and glycogen (amyloses) into sugars, _e. g._, ptyalin, diastase, amylopsin; _proteolytic_, those which change proteids into proteosis and peptones, _e. g._, trypsin, pepsin; _inversive_, those which change maltose, sucrose, and lactose into glucose, _e. g._, invertin; _coagulative_, those which change soluble proteids into insoluble, _e. g._, rennet; _steatolytic_, those which split up fats into fatty acids and glycerine, _e. g._, steapsin.
[32] A chemical change obtained by the action of sulphuric or some other acid, or by the influence of _diastase_.
[33] _Bacteriology and Infective Diseases_, Appendix.
[34] E. C. Hansen, _Studies in Fermentation_ (Copenhagen), p. 98.
[35] _Proc. Royal Soc. of Edin._, xxxvii., pt. iv., p. 759.
[36] E. A. Schäfer, _Text-book of Physiology_, vol. i., p. 25 (W. D. Halliburton).
[37] "Denitrifying" means reducing _nitrates_.
[38] R. Warington, M.A., F.R.S., _Journ. Roy. Agricultural Soc. Eng._, series iii., vol. viii., pt. iv., pp. 577 _et seq._
[39] The saltpetre beds of Chili and Peru are an excellent example of the industrial application of these facts. Nitrates are there produced from the fæcal evacuations of sea-fowl in such quantities as to form an article of commerce. A like form of utilisation of the action of these bacteria was once practiced on the continent of Europe. Economic application is also seen in the treatment of sewage referred to elsewhere.
[40] The course of nitrification may be followed by means of chemical tests. 1. The disappearance of ammonia. 2. The appearance of nitrite. 3. Its disappearance. 4. Appearance of nitrate.
[41] Professor Warington, in Report IV. (p. 526) of his admirable series of papers on the subject, draws attention to Müntz's criticism that the nitrifying organisms only oxidise from nitrogenous matter to nitrites, and not from nitrites to nitrates. Müntz held that the conversion of nitrite into nitrate is brought about by the joint action of carbonic acid and oxygen. Professor Warington's experiments, however, clearly illustrate that the production of nitrates from nitrites in an ammoniacal solution can be determined by the character of the bacterial culture with which the solution is seeded, and that in a solution of potassium nitrite conversion into nitrate can be determined by the introduction of the nitric organism. Professor Warington still adheres to the opinion, in favour of which he has produced so much evidence, that the formation of nitrates in the soil is due to the nitric organism which soil always contains.
[42] British Association for the Advancement of Science, Bristol, 1898, Presidential Address.
[43] British Association for the Advancement of Science, Bristol, 1898, Presidential Address.
[44] Sir John Lawes and Sir Henry Gilbert (_Times_, December 2, 1898), have pointed out that the addition of nitrates only would be of no permanent use to the wheat crop. They rely upon thorough tillage and proper rotation of crops as the means of improving the nitrogen value of the soil.
[45] Geddes, _Nature_, xxv., 1882.
[46] Sir Henry Gilbert, F.R.S., _The Lawes Agricultural Trust Lectures_, 1893, p. 129.
[47] _Ibid._, p. 140.
[48] This has been denied recently in the official report by the chemist of the Experimental Farm to the Minister of Agriculture at Ottawa (_Report_, 1896, p. 200).
[49] It has already been pointed out that the nitrifying bacteria, though able to live on organic matter, do not require such either for existence or for the performance of their function.
[50] Lehmann and Neumann, p. 305.
[51] The conditions requisite for an outbreak of enteric fever were, according to Pettenkofer, (_a_) a rapid fall (after a rise) in the ground water, (_b_) pollution of the soil with animal impurities, (_c_) a certain earth temperature, and lastly (_d_) a specific micro-organism in the soil. These four conditions have not, particularly in England, always been fulfilled preparatory to an epidemic of typhoid. Yet the observations necessary for these deductions were a definite step in advance of mere dampness of soil.
[52] _Supplement to the Report of the Medical Officer of the Local Government Board_, 1887, p. 7.
[53] _Report of Medical Officer to Local Government Board_, 1895-1896, Appendix.
[54] H. L. Russell, _Dairy Bacteriology_, p. 46.
[55] _Bureau of Animal Industry Reports_, 1895-1896.
[56] _British Medical Journal_, 1895, vol. ii., p. 322.
[57] _British Medical Journal_, 1895, vol. ii., p. 322.
[58] _Journal of Comparative Pathology_, vol. x. (1897), pp. 150-189.
[59] E. W. Hope, M.D., D.Sc., _Report of the Health of Liverpool during 1897_, p. 40.
[60] S. Rideal and A. G. R. Foulerton conclude, from a series of experiments, that boric acid (1-2,000) and formaldehyde (1-50,000) are effective preservatives for milk for a period of twenty-four hours, and that these quantities have no appreciable effect upon digestion or the digestibility of foods preserved by them (_Public Health_, May, 1899, pp. 554-568).
[61] _Report from Wisconsin Agricultural Experiment Station_, 1896.
[62] Jenner Institute of Preventive Medicine (First Series _Transactions_).
[63] _Centralblatt für Bakteriologie_, etc., II. Abteilung.
[64] _A Manual of Bacteriology, Clinical and Applied_, p. 397.
[65] Hewlett asserts that butter may contain from two to forty-seven millions of bacteria per gram.
[66] Such pure cultures for such purposes are in the United States termed "starters," because they start the process of special ripening. For the sake of convenience the term will be used here.
[67] The Essex County Council is one of the few public bodies in England which have undertaken pioneer work in this department of industry. Under the leadership of Mr. David Houston, a course of elementary instruction in dairy bacteriology as applied to modern dairy practice is given in the County Biological Laboratory at Chelmsford.
[68] _Report of Storr's Agricultural Experiments Station, State of Connecticut_, 1895.
[69] "Observations on Cheddar Cheese Making," _Reports of Bath and West and Southern Counties Society_, 1898, pp. 163-171. Mr. Lloyd's Reports to the West of England Society since 1892 contain various points respecting the application of bacteriology to cheese-making.
[70] _Journal of Bath and West of England Society_, 1893, 1895, and 1897.
[71] _New York Medical Record_, 1894.
[72] _British Medical Journal_, 1896, ii., p. 760 _et seq._
[73] _Special Report of the Medical Officer to the Local Government Board on Oyster Culture, etc._, 1896.
[74] Royal Commission on Tuberculosis, _Report_, 1895, pt. i., p. 13.
[75] _Ibid._, p. 18.
[76] _British Medical Journal_, 1895, vol. ii., p. 513.
[77] It should be distinctly understood that this table is merely schematic and provisional. The details of toxin production and its effect are still open to revision and amendment.
[78] Sidney Martin, M.D., F.R.S., F.R.C.P., _Croonian Lectures delivered before the Royal College of Physicians_, June, 1898.
[79] It is impossible here to enter into a detailed consideration of the various views held with regard to the formation of antitoxins. It is needless to remark that the whole matter is one of abstruse technicality and intricacy. These antitoxic bodies gradually increase in the blood and tissues, and their action falls into two groups: (_a_) _antitoxic_, which counteract the effects of the poison itself; and (_b_) _antimicrobic_, which counteract the effects of the bacillus itself. "In one and the same animal the blood may contain a substance or substances which are both antitoxic and antimicrobic, such, for example, as occurs in the process of the formation of the diphtheria and tetanus antitoxic serums" (Sidney Martin).
[80] Types of bodies possessing positive chemiotaxis for bacteria are the salts of potassium, peptone, glycerine.
[81] Negative chemiotaxis is illustrated in alcohol, and free acids, and alkalies.
[82] The friend of Addison and Pope, who married Mr. Edward Wortley Montagu in 1712, and on his appointment to the ambassadorship of the Porte in 1716 went with him to Constantinople. They remained abroad for two years, during which time Lady Wortley Montagu wrote her well-known Letters to her sister the Countess of Mar, Pope, and others.
[83] Crookshank, _History and Pathology of Vaccination_.
[84] An exhaustive account of vaccine may be found in the Milroy lectures delivered in 1898 at the Royal College of Physicians by S. Monckton Copeman, M.D.
[85] Crookshank, _Bacteriology and Infective Diseases_; Virchow, _The Huxley Lecture_, 1898.
[86] To shorten this period Dr. Cartwright Wood has adopted a plan by which time may be saved, and 200 cc. injected say within the first two or three weeks. This is accomplished by using a "serum toxin" (containing albumoses, but not ferments) previously to the broth toxin, an ingenious method which we cannot enter into here.
[87] At the conclusion of the operation the cannula is removed from the jugular vein, and the wound is closed by the valvular character of the slit in the skin and vein and the elasticity of the wall of the vein. No stitching or dressing is required. Indeed, it is striking to observe in the horse an entire absence of pain throughout the proceedings.
[88] The term _unit_ is used as a standard measurement. This means the amount of antitoxin which will just neutralise ten times the minimum fatal dose of the toxin in a guinea-pig (250 grams toxin to kill on the fourth day). If 1 cc. of the antitoxic serum is required for this, one unit is contained in 1 cc.; if 0.01 cc. is sufficient, then 100 units are contained in the cc. Not less than 1500 units should be administered for a dose, and repeated every twelve hours. In severe cases two or three times this amount may be given.
[89] The value of antitoxin treatment in diphtheria is discussed in the _Brit. Med. Jour._, 1899, pp. 197 and 268, by E. W. Goodall, M.D.
[90] A detailed study of tuberculosis from its pathological and bacteriological aspect will be found in _La Tuberculose et son Bacille_, pt. i., Straus, Professeur à la Faculté de Médecine de Paris.
[91] For differences of virulence between these conditions of pulmonary tubercle see Lingard, _Local Government Board Report_, 1888, p. 462.
[92] _Centralblatt. f. Bact. und Parasit._, vol. vii., p. 9.
[93] _Animal Tuberculosis_, p. 129.
[94] See the _Harben Lectures_, November, 1898, by Sir Richard Thorne Thorne, Medical Officer to the Local Government Board; also the _Report of the Royal Commission on Tuberculosis_, 1896-98.
[95] 1. Tuberculosis is a disease mainly affecting the lungs (_consumption_, _decline_, _phthisis_) of young adults and the bowels of infants (_tabes mesenterica_). It may affect any part of the body, and its manifestations are very various. It also affects animals, particularly cattle, by whom it may be transmitted to man.
2. _Its direct cause_ is a microscopic vegetable cell, known as the _Bacillus tuberculosis_, discovered by Koch in 1882. This fungus requires to be magnified some hundreds of times before it can even be seen. When it gains entrance to the weakened body it sets up the disease, which is an _infectious_ disease, though different in degree to the infectiousness of, say, measles.
3. _Trade influence and occupation_, in some cases, undoubtedly predispose the individual to tubercle. Cramped attitudes, exposure to dampness or cold, ill ventilation, and exposure to inhalation of dust of various kinds, all act in this way. In support of the evil effect of each of these four conditions much evidence could he produced.
4. _Overcrowding_ has a definite influence in propagating tubercular diseases. The agricultural counties without big towns, like Worcestershire, Herefordshire, Buckinghamshire, and Rutland, are the counties having the lowest mortality from tuberculosis; whilst the crowded populations in Northumberland, South Wales, Lancashire, London, and the West Riding suffer most. Speaking more particularly, the overcrowded areas of London, such as St. Giles', Strand, Holborn, and Central London generally, show very high tubercular death-rates.
5. _Tuberculosis is not increasing._ During the last thirty years it has shown, with few exceptions, a steady decline in all parts of England. "Consumption" is most fatal in comparatively young people (fifteen to forty-five years), whilst "tabes" and other forms of tubercle are fatal chiefly to young children. These forms have not declined so much as the lung form. The mortality in consumption of males has since 1866 been in excess of that of females. The age of maximum fatality from consumption is _later_ than in the past, which is probably due to improved hygiene and treatment.
6. _This decline has been due_, not to any special repressive measures--for few or none have been carried out--but to a general and extensive social improvement in the life of the people, to an increase of knowledge respecting tuberculosis and hygiene, to an enormous advance in sanitation, and to more efficient land drainage.
7. _Not all persons are equally liable to consumption_, some being much more susceptible than others. We have mentioned the predisposing influence of certain trades. There is also heredity, which acts, as we have said, in transmitting a tubercular _tendency_, not commonly the actual virus of the disease; there is, thirdly, the debilitating effect of previous illness or chronic alcoholism; there is, fourthly, the habitual breathing of rebreathed air; and, fifthly, there are the conditions of the environment, like dampness and darkness of the dwelling. Such influences as these weaken the resisting power of the tissues, and thus afford a suitable nidus for the bacillus conveyed in milk or by the inspiration of infected dust.
8. _Consumption is curable_ if taken in time. In cases where the lungs are half gone, and consist of large cavities, it is obvious that curability is out of the question. But if the disease can be properly treated in its earliest stages, there is considerable likelihood of recovery.
9. _The breath is not dangerous_, as far as we know, but there is danger from discharges of any kind from any infected part, whether lungs or bowels; for such discharges, when dry, may readily pollute the air, and either the bacilli or spores be inhaled into the lungs.
10. _The chief channels of personal infection or the spread of the disease amongst a community_ are two: (_a_) dried tubercular sputum (or other tubercular discharges); (_b_) infected milk or meat. So long as the former remains wet or moist, infection cannot take place. It is, of course, better to destroy it completely. As for milk and meat, boiling the former and thoroughly cooking the latter will remove all danger.
11. _The expectoration is infective._ This is one of the commonest modes of infection, and to it is held to be due the large amount of respiratory tuberculosis (consumption, phthisis). The expectoration from the lungs must contain, from the nature of the case, a very large number of bacilli. As a matter of fact, a single consumptive individual can cough up in a day millions of tubercle bacilli. When expectoration becomes dry, the least current of air will disseminate the infective dust, which can by that means be readily reinspired. Expectoration on pavements and floors, as well as on handkerchiefs, may thus become, on drying, a source of great danger to others. The discharges from the bowels of infants suffering from the disease also contain the infective material.
12. _Milk_, though a much more likely channel for conveyance of tubercle than meat, is only or chiefly virulent when the udder is the seat of tuberculous lesions. The consumption of such milk is only dangerous when it contains a great number of bacilli and is ingested in considerable quantity. Practically the danger from using raw milk exists only for those persons who use it as their sole or principal food, _e. g._, young children. All danger is avoided by boiling or pasteurising the milk.
At the same time there is an increasing amount of evidence forthcoming at the present time which goes to prove that milk is not infrequently tainted with tubercle (see p. 195). The tuberculin test should be applied to all milch cows, and the infected ones isolated from the herd. Milk supplies should be more strictly inspected even than cowsheds.
13. There are several methods by which _meat infection can be prevented_. In the first place, herds should be kept healthy, and tubercular animals isolated. Cowsheds and byres should be under sanitary supervision, especially as regards overcrowding, dampness, lack of light, and uncleanliness. Public slaughter-houses under a sanitary authority would undoubtedly be most advantageous. Meat inspection should also be more strictly attended to; efficient cooking, and avoidance of "roll" meat which has not been thoroughly cooked in the middle.
14. _Consumptive patients may diminish their disease._ Dr. Arthur Ransome[95a] has laid down five axioms of hygiene for phthisical patients which, if followed, would materially improve the condition of such persons. At Davos, St. Moritz, Nordrach and other places where they have been practised, the beneficial change has been in many cases extraordinary:
(1) Abundance of light, nutritious, easily digested food, which must comprise a large allowance of fat; small meals, but frequent;
(2) An almost entirely open-air life, with as much sunshine as can be obtained;
(3) Suitable clothing, mostly wool;
(4) Cleanliness and bracing cold-water treatment;
(5) Mild but regular exercise.
15. _Consumptive patients may also assist in preventing the spread of the disease._ In the first place, they should follow the hygienic directions just mentioned, because such conditions fulfilled will materially lessen the contagiousness of such patients; next, the expectoration must never be allowed to get dry. A spitting-cup containing a little disinfectant solution (one teaspoonful of strong carbolic acid to two tablespoonfuls of water) should always be used, or the expectoration received into paper handkerchiefs which can be burnt. Spoons, forks, cups, and all such articles should be thoroughly cleaned before being used by other persons. The patient should not sleep in company with another, but occupy, if possible, a separate bedroom.
Isolation hospitals for consumptives, as for patients suffering from diphtheria, are now being established.
16. _House influence_ has some effect, both directly and indirectly, upon tubercular diseases. Damp soils, darkness, and small cubic space in the dwelling-house exert a very prejudicial effect upon tubercular patients. Sir Richard Thorne Thorne[95b] has described the favourable house for such persons as one built upon a soil which is dry naturally or freed by artificial means from the injurious influences of dampness and of the oscillations of the underlying subsoil. The house itself should be so constructed as to be protected against dampness of site, foundations, and walls. Upon at least two opposite sides of the dwelling-house there should be enough open space to secure ample movement of air about it, and free exposure to sunlight. Lastly, it should be possible to have free movement of air by day and night through all habitable rooms of the house. It is clear that many inhabited houses could not stand to these tests; but effort should be made to approach as near to such a standard as possible.
17. _Sunlight and fresh air_ are the greatest enemies to infection.
18. _Disinfection is necessary after death from phthisis_, and should be as complete as after any other infective disease. Compulsory notification of fatal cases and compulsory disinfection have been officially ordered by the Prussian Government. In this country also absolute disinfection should always be insisted upon after phthisis. Walls, floors, carpets, curtains, etc., should be strictly sterilised. Professor Delepine recommends spraying with 1-100 solution of chloride of lime.
[95a] Arthur Ransome, M.D., F.R.S., _Treatment of Phthisis_.
[95b] _Practitioner_, vol. xlvi.
[96] _Journal of State Medicine_, vol. iv. (1896), p. 169.
[97] For a fuller statement see _Trans. Jenner Institute_ (First Series), pp. 7-32.
[98] See _Trans. Jenner Institute_ (First Series), A. G. R. Foulerton, pp. 40-81.
[99] Dated 1890-91. The Commissioners were the late Beaven Rake, M.D., G. A. Buckmaster, M.D., the late Professor Kanthack, of Cambridge, the late Surgeon-Major Arthur Barclay, and Surgeon-Major S. J. Thomson.
[100] _Bacteriology and Infective Diseases_ (1896), p. 144. Professor Crookshank's Reports to the Agricultural Department of the Privy Council constitute the most complete account of this disease hitherto published.
[101] _Zeitschr. f. Hyg. und Inf. Krank._, xxv.
[102] _Journal of State Medicine_, December, 1897, p. 561.
[103] _Bacteriology and Infective Diseases_, p. 35.
[104] _British Medical Journal_, 1895 (February), p. 353.
[105] _British Medical Journal_, 1896 (August), p. 439.
[106] _Journal of State Medicine_, 1898 (November), p. 541.
[107] The measurement of cubic space is of course made by multiplying together in feet the length, breadth, and height of a room.
[108] _British Medical Journal_, 1898 (April), p. 1013.
INDEX
Abscess formation, 296-301
Acetous fermentation, 115, 127
Actinomycosis, 316
Aërobic organisms, 26
Agar, 21
Air, bacteriology of, 96-110
-- examination of, 96-99
-- of sewers, 105
-- expired, 102
-- bacteria and gravity, 106
-- standard of bacteria in, 108
-- pathogenic bacteria in, 109
-- passages, bacteria in, 103
Alcohol, formation of, 115
Alcoholic fermentation, 115, 117
Alexines, 249, 268
Alformant lamp for disinfection, 334
Algæ in water, 53
Ammoniacal fermentation, 115
Amylolytic ferments, 115
Anaërobic organisms, 132
-- methods of culture, 139-142
-- in hydrogen, 139, 140
-- in glucose-agar, 142
-- in Fränkel's tube, 140
-- in Buchner's tube, 141
Aniline dyes, 44
Antagonism of organisms, 33
Anthrax, 19, 26, 30, 34, 245
-- pathology of, 301
-- spores of, 302
-- bacillus of, 302
Antiseptics, 323, 332
-- definition of, 322
-- some of the chief, 332
Antitoxins, 245-250
-- preparation of, 259
-- use of, 263
-- unit of, 263
Appendix, 337
Arthrospores, 17
Artificial purification of water, 73
Ascospores, 120
Asiatic cholera, 65
Association of organisms, 31
Attenuation of virulence, 36
Bacillus, definition of, 11
-- aceti, 34, 129
-- acidi lactici, 131, 185, 190
-- amylobacter, 132
-- anthracis, 26, 31, 34, 110, 301-305
-- aquatilis, 53
-- butyricus, 133
-- coli communis, 32, 56, 58-62, 64, 67, 86, 88, 108, 151, 194, 237, 299, 315
-- cyanogenus, 193
-- diphtheriæ, 201, 212, 244, 289-296
-- enteriditis sporogenes, 60, 86, 87, 316
-- erythrosporus, 53
-- fluorescens liquefaciens, 43, 53, 64, 86
-- fluorescens non-liquefaciens, 53, 15
-- of cholera, 65-69
-- of diarrhœa, 203, 204
-- of influenza, 315
-- lactis erythrogenes, 193
-- lactis pituitosi, 193
-- lactis viscosus, 193
-- liquefaciens, 53, 151
-- of leprosy, 308-313
-- of glanders (mallei), 299, 319
-- mesentericus, 86, 151
-- mycoides, 151
-- of malignant œdema, 19, 172
-- No. 41, 219
-- pasteurianum, 130
-- of scarlet fever, 202
-- of symptomatic anthrax, 19, 171, 172
-- of plague, 306-308
Bacillus prodigiosus, 34, 151, 193, 238
-- pyocyaneus, 7, 34, 64, 110, 299
-- pyogenes fœtidus, 34
-- radicicola, 164
-- saponacei, 193
-- subtilis, 31, 86, 108
-- synxanthus, 194
-- of tetanus, 19, 168-171
-- termo, 53
-- of tubercle, 110, 212, 225, 274-291
-- typhosus, 41, 50, 55-62, 212
-- ubiquitous, 53
-- of yellow fever, 316
Bacteria, action of, 26
-- in sewage, 84
-- and wheat supply, 161
-- and fixation of nitrogen, 160-166
-- in cheese-making, 220-227
-- in the dairy, 215-227
-- products of, 240, 241
-- and disease, 264-321
-- the higher, 11, 33
-- in soil, 137-177
Bacterial action, 26
-- treatment of sewage, 90
Bacteroids, 166
Beer diseases, 134
Berkefeld filter, 52
Biogenesis, 3
Biology of bacteria, 1-36
Bitter fermentation, 191
Blood serum, 22
Blue milk, 193
Boracic acid, 205, 331
Bread, bacteria in, 238
Broth, 21
Brownian movement, 14
Bubonic plague, 306-308
Buchner's tube, 141
Butter, bacteria in, 213, 214
-- examination of, 214
-- bacterial flavouring of, 215
Butyric fermentation, 115, 132, 191
Carbol-fuchsin, 44
Carbol-gelatine, 62
Carbolic acid as a germicide, 332
Caries, dental, 104
Chamber, moist, 41
Channels of infection in disease, 269
-- in tubercle, 289
Cheese, bacteria in, 220
Chemical products of bacteria, 241
Chemical substances as disinfectants, 329
-- and bacteriological examination of water compared, 51
-- tests for nitrification, 158
Chemiotaxis, 15, 248
Chicken cholera, 320
Chinosol as a disinfectant, 336
Chloride of lime as a germicide, 331
Cholera, 65-68
-- diagnosis of, 68
-- and filtration, 75
-- and milk, 200
Chromogenic bacteria, 193, 241
Cladothrix, 8, 33
Clark's process, 73
Classification, 7
Coccus, definition of, 8
Colon bacillus, _see_ B. coli communis
Comma bacillus, 66
Commensalism, 162
Composition of bacteria, 12-14
Conditions affecting bacteria in water, 70
-- in milk, 186, 187
Contagion, 270
Corrosive sublimate as disinfectant, 331
Counter (Wolfhügel), 49
Cover-glass preparations, 44
Cream, bacteria in, 213
Crenothrix polyspora, 53
Creosol as a germicide, 332
Cultivation beds, 92
Culture media, 20
-- anaërobic, 139
-- hanging drop, 44
-- plate, 40-43
-- pure, 20, 46
-- shake, 62
Decomposition bacteria, 149
Denitrifying bacteria, 143, 149
Dental caries, 104
Deodorants, 323
Desiccation, 26
Diagnosis, 339
Diarrhœa of infants, 175, 316
Diphtheria, 243-245, 289-296
-- bacillus of, 289
-- toxins of, 244, 293
-- and milk supply, 201
-- and school influence, 294, 295
-- pseudo-bacillus of, 296
Diplococcus, definition of, 8
Diplococcus of gonorrhœa, 300
-- in pneumonia, 313
Directions for estimating disinfectants, etc., 324
Disease, production of, 264
Diseases of beer, 134
-- of plants, 35
-- of animals, 316-320
-- conveyed by water, 81
-- and soil, 173-177
Disinfectants, 322, 331
Disinfection, 322-336
-- of a room, 335
-- of walls, 335
-- of bedding, 335
-- of garments, 335
-- of excreta, 335
-- of wounds, 336
-- of hands, 336
Domestic purification of water, 79
Dunham's solution, 69
Dysentery, 319
Earth temperatures and disease, 175
Economic bacteria, 145
Egg cultures, 340
Elsner's medium, 62
Endospores, 17
Enteric fever, _see_ Typhoid
Enzymes, 114
Equifex disinfector, 328
-- sprayer, 334
Erysipelas, 299
Examination, bacteriological--
-- air, 96-99
-- cholera, 68
-- diphtheria, 290, 340
-- leprosy, 309
-- meat, 234
-- milk, 227
-- sewage, 80
-- soil, 138
-- tetanus, 170
-- tubercle, 276, 339
-- water, 43-48
-- yeasts, 119, _et seq._
Extracellular poisons, 244, 273
Fermentation, 111-136
-- acetous, 115, 127
-- alcoholic, 115, 117
-- ammoniacal, 115, _see_ under Soil
-- butyric, 115, 132, 191
-- lactic acid, 115, 130, 190
Ferments, organised, 114, 115
Ferments, unorganised, 114, 115
-- chromogenic, 193
-- curdling, 191
-- bitter, 191
-- slimy, 192
-- soapy, 193
Films, 123
Filter, domestic, 79
Filter-beds, 74
Filtration, milk, 206
-- method of air examination, 99
-- sand, 77-79
Fission, 16
Fixing specimens, 45
Flagella, 15
-- staining, 63
Food, bacteria in, 179, 180
Foot-and-mouth disease, 320
Formaldehyde and formalin, 205, 206, 333
Forms of bacteria, 8
Fränkel's tube, 140
-- pneumococcus, 314
Friedländer's pneumo-bacillus, 315
Gas, production of, 62, 241
Gathering-ground, 38
Gelatine, 21
-- carbol, 62
-- liquefaction of, 44
Gemmation, 119
Gentian-violet, aniline, 44
Germicidal temperatures, 30, 207
Germicides, 322, 331
Glanders, 319
Gonorrhœa, 300
Gram's method, 44, 338
Gravity, influence on bacteria, 106
Gypsum block, 121
Hæmatozoa, 320
Hanging drop cultivations, 44
Hansen's method of dilution, 123
Heat as steriliser, 30, 326
Heredity, 268, 269
Hesse's method of air examination, 98
Higher bacteria, 11
High yeasts, 125
Hot air steriliser, 31
Hydrogen cultivation, 139
Hydrophobia, treatment of, 253
Ice-cream, bacteria in, 236-238
-- examination of, 236
Immunity, 240-263
-- acquired, 247, 250
-- active, 250
-- artificial, 250
-- natural, 250
-- passive, 250
Incubation period, 271
Incubators, 22
Indol, formation of, 61
-- testing for, 61
Industries and bacteria, 135
Influenza, 315
Intracellular poisons, 34
Inversive ferments, 115
Involution forms, 12, 66
Kipp's apparatus for producing hydrogen, 27, 139
Klebs-Löffler bacillus, 289
Koch's plate method, 40
-- postulates, 266
-- comma bacillus, 66
-- bacillus of tubercle, 276
Lactic acid fermentation, 115, 130, 185, 190, 221, 226
Lactose, 190
Leguminosæ, fixation of nitrogen by, 163
Leprosy, 308-313
Leptothrix, 8, 33
Leuconostoc, 17
Light, influence upon bacteria, 24-26, 70
Liquefaction of gelatine, 44, 241
Low yeasts, 125
Lymph, glycerinated calf, 252
Lyon's, Washington, disinfector, 328
Maceration industries, 135
Malaria, 177, 320
Malignant œdema, 19, 172
Mallein, 319
Mastitis, 184
Measles, 321
Meat, 234
Media, culture, 20
Merismopedia, 11
Method of examination, 43-47
Metropolitan water supply, 72
Miasmatic diseases, 176
Micrococcus, definition of, 8
-- agilis, 16
-- aquatilis, 53
-- casei amari, 226
Micrococcus Freudenreichii, 192
-- gonorrhϾ, 299
-- tetragonus, 299
-- viscosus, 192
Milk, bacteriology of, 178-213
-- absorptivity of, 180
-- sources of pollution, 181-184
-- number of bacteria in, 185
-- influence of temperature upon, 186
-- influence of time of standing, 187
-- fermentation bacteria in, 189
-- constitution of, 189-195
-- disease-producing power of, 195
-- and tuberculosis, 197-199, 228, 290
-- and typhoid, 199
-- and cholera, 200
-- and diphtheria, 201
-- and scarlet fever, 202
-- and thrush, 203
-- methods of preservation of, 205
-- and added antiseptics, 205, 206
-- filtration of, 206
-- sterilisation of, 207
-- pasteurisation of, 208-213
-- products, bacteria in, 213-227
-- examination of, 227
-- and economic bacteria, 215-220
-- sterile, 181
-- kinds of bacteria in, 188
-- chromogenic, 193
-- cooling processes, 207, 209
Moist chamber, 41
Moisture necessary for bacteria, 23
Motility, 14
Moulds, 116
Mycoderma aceti, 127
Nasal passages, bacteria in, 103
Natural purification of water, 69
Needles, platinum, 22, 24
Nitrates, 147, 154
Nitric organism, 157, 158
Nitrification, 76, 143-159
-- chemistry of, 144-148
-- stages in, 145
-- bacteria of, 152
Nitrifying organisms, cultivation of, 156
Nitrogen, fixation of, 144, 160-168
Nitrous organism, 154, 158
Nodules on roots, bacteria in, 163
Oidium albicans, 203
Oxygen necessary for bacteria, 26
Oysters and bacteria, 229-234
Paraform for disinfection, 334
Parasitism, 27, 162
Parietti's method, 62
Pasteurisation of milk, 208-213
Pasteur's treatment of rabies, 253-258
Perlsucht, 283
Petri dishes, 50
Phagocytosis, 247
Phosphorescence, 26, 241
Pigment, formation of, 241
Place of bacteria in nature, 5
Plague, 306-308
Plant diseases, 35
Plate cultures, 40-46
Platinum needles, 22, 24
Pleomorphism, 12
Pneumo-bacillus, 315
Pneumococcus, 313
Pneumonia, 313
Polymorphism, 12
Postulates, Koch's, 266
Potato medium, 22
Pouchet's aëroscope, 96
Proteolytic ferments, 115
Proteus family, 86, 180, 297
-- vulgaris, 60, 86, 151, 194
-- zenkeri, 60
Pseudo-diphtheria bacillus, 296
Ptomaines, 179
Pure culture, 20, 46
Purification of water--
-- natural, 69
-- artificial, 73
Pus, 296
Putrefaction, 143-149
Pyocyanin, 299
Pyoxanthose, 299
Quantitative standard for water bacteria, 48, 49
-- air bacteria, 107
-- milk bacteria, 188
-- soil bacteria, 137
Quarter evil, 19, 171
Rabies, treatment of, 253
-- forms of, 253
-- pathology of, 254
-- results of treatment, 256
Reck's disinfector, 328
Reproduction of bacteria, methods of, 16
Retting, 135
Rinderpest, 320
Saccharomycetes, biology of, 119-121
-- methods of examination, 122
-- anomalous, 122
-- apiculatus, 127
-- aquifolii, 127
-- cerevisiæ, 117, 124, 126
-- conglomeratus, 126
-- ellipsoideus I., 126
-- ellipsoideus II., 126, 134
-- exiguus, 127
-- Hansenii, 127
-- illicis, 127
-- Ludwigii, 122
-- mycoderma, 127
-- pastorianus I., 127, 134
-- pastorianus II., 127
-- pastorianus III., 127, 134
-- pyriformis, 127
Salicylic acid as antiseptic, 205, 206
Saprophytes, 27, 166
Sarcina, 10
Scarlet fever, 202, 321
Sedgwick's method of air analysis, 99
Sedimentation, 71, 73
Septic processes, 296
-- tank, 90
Sewage, organisms in, 84
-- bacterial treatment of, 89
Sewer air, 87
-- and toxicity of bacteria, 105
Shake culture, 62
Shell-fish and bacteria, 229, 234
Small-pox, 251, 321
Soil, bacteriology of, 137
-- examination of, 138
-- kinds of bacteria in, 142-145
-- and its relation to disease, 173, 176, 177
Species of bacteria, 29
Spirillum, definition of, 11
-- of cholera, 66
Spontaneous generation, 2
Spores, kinds of, 17-19
-- resistance of, 19, 278
-- staining of, 19
-- of yeasts, 122
Staining methods, 45
Staphylococcus, 10, 296
-- cereus albus, 297
-- pyogenes aureus, 88, 108, 297
Steam as a disinfector, 326
-- disinfectors, 327-329
-- steriliser, 326
-- saturated, 327
-- superheated, 327
Steam current, 327
Sterilisation, 29-31
-- methods of, 30, 31
Streptococcus, 9, 297
-- pyogenes, 299
-- Hollandicus, 192
Streptothrix, 317
Structure of bacteria, 8
Sulphurous acid as a germicide, 332
Suppuration, 296-301
Swine fever, 320
Symbiosis, 162
Symptomatic anthrax, 171
Table of economic bacteria in soil, 145
Temperature, influence of, on bacteria, 23
Tetanus, 19, 168, 245
-- toxin of, 168
Thresh's disinfector, 328
Thrush, 203
Tissues, effect of, on bacteria, 267
Tobacco-curing, 136
Toxins, 28, 241-247, 272
Tuberculin, 281
Tuberculosis, 274-292
-- pathology of, 274
-- varieties of, 275
-- history of, 276
-- conveyed by the air, 104
-- and the milk supply, 196-198, 290
-- giant cells in, 275
-- bacillus of, 276
-- cultivation of bacillus of, 277
-- spores of, 277
-- relation of bacillus to disease, 279
-- toxins of, 281
-- of animals, 283
-- prevention of, 286-292
-- disinfection in cases of, 292
-- decline of, 288
-- and overcrowding, 288
-- channels of infection in, 289
-- expectoration in, 290
Tuberculosis and house influence, 291
-- and glanders, 319
Typhoid fever, 56
-- bacillus of, 55-58
-- micro-pathology, 57
-- bacillus compared with B. coli, 58
-- bacillus in sewage, 59
-- bacillus in drinking water, 60
-- tests for bacillus of, 61-64
-- and soil, 173, 176
-- conveyed by the air, 105
-- and milk supply, 199
Tyrotoxicon, 205, 237
Unit of antitoxin, 263
Urea, 148
Vaccination, 251-253
Vaccines, plague, 257, 259
-- cholera, 257
-- small-pox, 251
Vaccinia, 251
Variolation, 250, 251
Virulence increased, 32
-- diminished, 36
Water, bacteria in, 37-84
-- number of bacteria in, 38
-- examination of, 39-52
-- disease organisms found in, 55
-- natural purification of, 69
-- artificial purification of, 73
-- filtration of, 74
-- domestic purification of, 79
-- pollution of, 82
Wheat supply and bacteria, 161
Widal reaction, 63, 340
Wooden tongue, 318
Wool-sorters' disease, 305
Yeasts, 116
Yellow fever, 316
Ziehl-Neelsen stain, 44, 340
The Science Series
Edited by Professor J. MCKEEN CATTELL, Columbia University, with the cooperation of FRANK EVERS BEDDARD, F.R.S., in Great Britain.
Each volume of the series will treat some department of science with reference to the most recent advances, and will be contributed by an author of acknowledged authority. Every effort will be made to maintain the standard set by the first volumes, until the series shall represent the more important aspects of contemporary science. The advance of science has been so rapid, and its place in modern life has become so dominant, that it is needful to revise continually the statement of its results, and to put these in a form that is intelligible and attractive. The man of science can himself be a specialist in one department only, yet it is necessary for him to keep abreast of scientific progress in many directions. The results of modern science are of use in nearly every profession and calling, and are an essential part of modern education and culture. A series of scientific books, such as has been planned, should be assured of a wide circulation, and should contribute greatly to the advance and diffusion of scientific knowledge.
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G. P. PUTNAM'S SONS, NEW YORK & LONDON
THE SCIENCE SERIES
(Volumes ready, in press, and in preparation.)
+The Study of Man.+ By Professor A. C. HADDON, M.A., D.Sc., Royal College of Science, Dublin. Illustrated. 8^o, $2.00
+The Groundwork of Science.+ A Study of Epistemology. By ST. GEORGE MIVART, F.R.S. 8^o, $1.75
+Rivers of North America.+ A Reading Lesson for Students of Geography and Geology. By ISRAEL C. RUSSELL, LL.D., Professor of Geology in the University of Michigan. Illustrated. 8^o, $2.00
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+Bacteria.+ By G. NEWMAN, M.D., F.R.S., Demonstrator of Bacteriology in King's College, London. Illustrated. 8^o.
+The Stars.+ By Professor SIMON NEWCOMB, U.S.N., Nautical Almanac Office, and Johns Hopkins University.
+Meteors and Comets.+ By Professor C. A. YOUNG, Princeton University.
+The Measurement of the Earth.+ By Professor T. C. MENDENHALL, Worcester Polytechnic Institute, formerly Superintendent of the U. S. Coast and Geodetic Survey.
+Earthquakes.+ By Major C. E. DUTTON, U.S.A.
+Physiography; The Forms of the Land.+ By Professor W. M. DAVIS, Harvard University.
+The History of Science.+ By C. S. PEIRCE.
+General Ethnography.+ By Professor DANIEL G. BRINTON, University of Pennsylvania.
+Recent Theories of Evolution.+ By J. MARK BALDWIN, Princeton University.
+Whales.+ By F. E. BEDDARD, F.R.S., Zoölogical Society, London.
+The Reproduction of Living Beings.+ By Professor MARCUS HARTOG, Queen's College, Cork.
+Man and the Higher Apes.+ By Dr. A. KEITH, F.R.C.S.
+Heredity.+ By J. ARTHUR THOMPSON, School of Medicine, Edinburgh.
+Life Areas of North America: A Study in the Distribution of Animals and Plants.+ By Dr. C. HART MERRIAM, Chief of the Biological Survey, U. S. Department of Agriculture.
+Age, Growth, Sex, and Death.+ By Professor CHARLES S. MINOT, Harvard Medical School.
+Bacteria.+ Dr. J. H. GLADSTONE.
+History of Botany.+ Professor A. H. GREEN.
+Planetary Motion.+ G. W. HILL.
+Infection and Immunity.+ GEO. M. STERNBERG, Surgeon-General U.S.A.