Part 33
=AMYLA'CEOUS= ([)a]m-e-l[=a]'-sh'[)u]s). _Syn._ AMYLA'CEUS, L.; AMYLACÉ, Fr. Of or like starch; consisting of or abounding in starch; starchy. See FOOD, NUTRITION, STARCH, &c.
=AM'YL= (-[)i]l). C_{5}H_{11}. The radical of the fusel-oil compounds (AMYL-SERIES).
=Amyl, Acetate of.= C_{5}H_{11}C_{2}H_{3}O_{2}. _Syn._ PEAR-OIL. _Prep._ From fusel-oil, 1 part; acetate of potassa (dry), 2 parts; concentrated sulphuric acid, 1 part; distilled, with the usual precautions, from a glass retort into a cool receiver. The distillate is purified by washing it with very dilute solution of potassa, and redistilling it from fused chloride of calcium. A little litharge added to the liquid in the retort, before rectification, will remove any sulphurous odour, should it be present.
_Prop., &c._ Liquid, limpid, colourless; insoluble in water; soluble in alcohol; boils at 272° Fahr.; alcoholic solution of potassa converts it into an acetate of that base, with reproduction of fusel-oil.
_Obs._ The odour and flavour of this preparation are those of the Jargonelle pear. It is now extensively manufactured, and, after dilution with alcohol, is sold under the name of ESSENCE OF JARGONELLE PEAR, for flavouring liqueurs and confectionery.
=Amyl, Vale'rianate of.= C_{5}H_{11}C_{5}H_{9}O_{2}. _Syn._ APPLE-OIL, A.-ESSENCE, &c. This compound is abundantly formed during the preparation of valerianic acid from potato oil, and is recognised by the offensive odour of rotten apples evolved during the process. By treating the crude product of the distillation with a weak solution of pure potassa, the valerianic acid is removed, and the volatile oil obtained nearly pure. Dissolved in rectified spirit it forms the 'APPLE-ESSENCE' now so much employed as a flavouring ingredient for confectionery and liqueurs. See FRUIT ESSENCES, VALERIANIC ACID, &c.
=AMYL NITRITE.= _Syn._ AMYL NITRIS, B. P. Produced by the action of nitric or nitrous acid on amylic alcohol.--_Dose._ By inhalation, the vapour of 2 to 5 minims. To be used with caution. It may be produced by passing a stream of nitrous acid gas through purified amylic alcohol at a temperature of 132° C.
For other methods of preparing it consult 'Wood and Bache's United States Dispensatory, 1877.' Mr Umney ('Pharm. Journal') says that true nitrite of amyl should be made by passing nitrous acid into amylic alcohol which has been previously submitted to a fractional distillation, until the portion retained for use has a boiling point of 132° C. A nitrate so prepared, when deprived of any excess of acid it may contain by rectification over fused carbonate of potash, will have a boiling point of 98°-99° C.
=AM'YLENE= (-e-l[=e]ne). C_{5}H_{10}. [Eng., Fr.] _Syn._ AM'ILENE*; AMYLE'NA, AMYLE'NUM, L. A peculiar volatile, liquid hydrocarbon, discovered by Cahours.
_Prep._ From fusel-oil repeatedly distilled along with either anhydrous phosphoric acid, or a concentrated solution of chloride of zinc; the product being repeatedly rectified at a low temperature, until the boiling point sinks to 102° Fahr.
_Prop., Uses, &c._ An ethereal liquid, lighter than water, having an aromatic odour, slightly alliaceous. Sp. gr. of vapour, 2·68. Its vapour was several times successfully employed, by the late Dr Snow, as a substitute for ether and chloroform in producing anæsthesia, being, though less agreeable, also less pungent, and consequently easier to breathe, than either of them; but its use has since been given up owing to doubts as to its safety, two or three deaths having followed its inhalation.
=ANADOLI= (Kreller, Nuremburg). An oriental tooth-powder. Powdered soap, 42 parts; starch powder, 44 parts; levantine soapwort, 12 parts; oil of bergamot and lemon to flavour. (Wittstein.)
=ANÆMIA.= Deficiency of blood.
=ANÆSTHE'SIA= ([)a]n-[=e]z-the'-zh'[)a]; -sh'[)a]; -th[=e]ze'y'[)a]r). [L.; prim. Gr.] _Syn._ ANESTHÉSIE, Fr. In _pathology_, diminished or lost sense of feeling.
In _surgery_ and _obstetrics_, the production of temporary anæsthesia, for the purpose of rendering operations painless, relieving the pangs of childbirth, &c., is effected by the use of--
=ANÆSTHET'ICS.= _Syn._ ANÆSTHET'ICA, L.; ANESTHÉTIQUES, Fr. In _pharmacology_ and _surgery_, substances or agents which diminish or destroy sensibility, or which relieve pain. In its full extent this term includes both anodynes and narcotics; but it is now more generally confined to those substances which greatly diminish common sensibility, or entirely remove susceptibility to pain. Among the most useful, safe, and powerful of this class are chloroform, ether, nitrous oxide, and intense cold; besides several chlorinated compounds, such as the bichlorides of ethylen, methylen, and carbon.
More than 1500 years ago the Chinese are said to have used a preparation of hemp, or _ma-yo_, to annul the pain attendant upon cauterisation and other surgical operations. Mandragora (mandrake) was employed for a similar purpose by the Greeks and Romans; and we learn that as early as the thirteenth century the vapour from a sponge filled with tinctures of mandragora, opium, and other sedatives was used for a similar purpose.
Baptista Porta, in his work on natural magic printed in 1597, mentions a quintessence extracted from medicines by somniferous menstrua, of the nature of which he leaves us in ignorance. This quintessence was to be preserved in leaden vessels very perfectly closed, lest the aura should escape, for the medicine would vanish away. Furthermore, he adds, "when it is used, the cover being removed, it is applied to the nostrils of the sleeper, who draws in the most subtle power of the vapour by smelling, and so blocks up the fortress of the senses, that he is plunged into the most profound sleep, and cannot be roused without the greatest effort." Dr Iron suggested that the volatile substance was sulphuric ether, which he says had been described more than fifty years before Porta wrote his book. In the year 1800 Sir Humphry Davy suggested the employment of nitrous oxide, or laughing gas, as it was then termed, for minor operations in surgery, and in 1828 Dr Hickman proposed carbonic acid as an anæsthetic. The vapour of sulphuric ether had been used in his practice by Dr Pearson as early as 1795, for the relief of spasmodic asthma. The fact that sulphuric ether was capable of producing insensibility was demonstrated by American physicians; viz. by Godwin in 1822, Mitchell in 1832, Jackson in 1833, and Wood and Bache in 1834; but the first practitioner to employ it to prevent the pain of an operation was Dr Morton, a Boston dentist, who successfully used it for this purpose in 1846. On the 19th of December of the same year Mr Liston, of University Hospital, London, and Mr Robinson, a dentist, operated upon patients who had been rendered insensible by means of the inhalation of the vapour of ether.
Throughout the year 1847 ether was employed as an anæsthetic both in England and France, but towards the end of that year the anæsthetic properties of chloroform were pointed out by Flourens. The first, however, to introduce this agent into surgical and obstetric practice was Dr I. T. Simpson, of Edinburgh. In 1849 a work on the inhalation of ether was published by Dr Snow, who afterwards introduced a new anæsthetic, viz. amylene, which was capable of producing effects similar to those of chloroform; but as two patients out of but a small number who inhaled the vapour of amylene died, this latter soon fell into discredit, and consequent disuse.
Except in dental practice, in which nitrous oxide gas is the anæsthetic invariably employed, chloroform is almost universally used in surgical operations, one advantage it possesses over ether being its much more rapid action, although this latter property must be regarded as one which constitutes the risk which, although very slight (when the exceedingly small per-centage of deaths resulting from its administration is taken into account), undoubtedly attends its inhalation.
Dr Sansom says of chloroform:--"The cause of its danger is its power of paralysing the cardiac and other motor sources of circulation. This property resides in large and sudden doses of its vapour." He strongly recommends its dilution by air and alcohols. He further remarks that all anæsthetics modify the endosmotic condition of the blood discs, and contends that they affect the supply of arterial blood by altering the calibre of the channels which convey it. He advocates the substitution of one anæsthetic for another during the inhalation.
Methylene dichloride, introduced by Dr B. W. Richardson, is said to possess the disadvantage of causing considerable depression.
The mode of administering these agents is by causing the patient to inhale their vapour mixed with air.
Sometimes they are poured on to a sponge or a handkerchief, or piece of lint, either of which is then applied to the mouth and nostrils of the patient in such a manner that the air which passes into his lungs is saturated with the vapour. Except in extemporised cases, however, this method is pretty well abandoned, a proper apparatus having supplanted the sponge or handkerchief, &c. Part of the apparatus consists of a graduated bottle containing the anæsthetic, by means of which the operator is enabled to tell how much of this latter is being consumed, and thus to regulate the quantity inhaled.
The first effect that results from the administration of anæsthetics is a form of intoxication, caused by the action of the anæsthetic agent on the cerebral lobes, and as this action extends to the cerebellum, the patient becomes incapable of directing his movements--an effect like that caused by intoxication from alcohol.
In the next stage the spinal cord is attacked, unconsciousness supervenes, and all powers of motion and sensation are lost. The individual is now said to be in a state of anæsthesia; but the heart continues to beat, respiration is not impeded, and the other essential functions of the body go on as usual.
Should, however, the exhibition of the anæsthetic agent be incautiously continued too long, the bodily temperature falls, the movements of respiration and circulation become impaired, the heart ceases its action, and death finally ensues. The introduction of anæsthetics into surgical practice has been of great and invaluable service to the operator. The patient being motionless and free from pain, the surgeon is enabled to perform the operation at his ease, and consequently more efficiently; moreover, in the reduction of dislocations and of hernia, the muscles being flaccid, the obstacle produced by their contraction is removed. M. Velpeau endeavoured to produce local anæsthesia, or insensibility of the part of the body to be operated upon, by means of a freezing mixture composed of ice and salt; this method, however, was found impracticable, and was soon abandoned. Since then local anæsthesia as introduced by Dr Richardson, when had recourse to, is effected by means of a spray of ether directed on the part, the intense cold produced by the rapid evaporation of the ether entirely depriving the part of sensation. It is said that the pain resulting from the application of this method is a great barrier to its use.
Amongst anæsthetics, nitrous oxide gas occupies an important place, its use, as before stated, being almost wholly confined to operations in dental surgery.[55] As in the case of ether, the American practitioners were the first to employ nitrous oxide as an anæsthetic. Attention was directed to its anæsthetic properties in 1844 by Mr Horace Wells, an American dentist, but little interest seems to have been awakened by his application of it, since it was not until 1863 that Dr Cotton, of New York, drew attention to the subject by performing an operation on a patient under its influence.
[Footnote 55: The 'British Medical Journal' for 1868 states it was used successfully at the Ophthalmic Hospital, Moorfields.]
In March, 1868, Dr Evans, residing in Paris, after a visit from Dr Cotton, directed the attention of medical men in England to the value of nitrous oxide as an anæsthetic in dental surgery, and shortly afterwards it was first employed to produce anæsthesia at the Dental Hospital. Nitrous oxide is obtained from nitrate of ammonia, and the particulars of its preparation may be found by referring to the article NITROUS OXIDE.
Immense quantities of the gas are used in dental operations. It has been computed that in 1870 Messrs Coxeter and Barth could not have prepared much less than 60,000 gallons in London alone. To fit it for transit it is reduced by compression. Fifteen gallons may thus be diminished in volume until it fills an iron bottle holding a quart. Five or six gallons of the gas are, on an average, required for each patient. In the preparation of nitrous oxide for surgical purposes Dr Evans advises it to be made at least 24 hours before it is used, and further recommends its being thoroughly washed. An apparatus for the preparation of the gas was devised by Mr Porter, a description of which will be found in the 'Transactions of the Odontological Society of Great Britain' for 1868, in which also mention is made of a face-piece for its administration, the invention of Mr Clover. By means of this latter instrument the desiderata that the nitrous oxide should be inhaled without admixture with atmospheric air, and contamination arising from the expired air given off by the patient, are accomplished, for it has been found that when excitement and talking attend the inhalation of the gas, these effects are due to the presence of the carbonic acid thrown off by the lungs.
When inhaled in the ordinary way, nitrous oxide gas induces exhilaration and narcotism, without asphyxia. When, however, the atmospheric air is carefully excluded, it produces, as we have just seen, anæsthesia without exhilaration. The time required to produce anæsthesia varies from 25 to 120 seconds, by from 10 to 60 inhalations. A patient has been subjected for 10 minutes to its action without experiencing any unpleasant symptoms or after effects. Mr Randle says it is perfectly safe in all short operations, and possibly in long ones also, provided there is due admission of air at proper intervals. It seems tolerably certain that nitrous oxide is largely absorbed by the blood-corpuscles, and it is probable that its presence in them may temporarily act to the exclusion of oxygen, and thus prevent for a time that combination of oxygen with hæmoglobin upon which the red colour of the corpuscles depends. Chemistry, however, has failed to show that nitrous oxide is decomposed in the blood, or that it exerts any of the chemical properties of oxygen on the constituent elements of the blood. Whenever the slightest anæsthetic effect is communicated to the nervous system, a simultaneous effect is produced upon the medulla oblongata, the spinal chord, as well as upon the cerebrum and cerebellum.
The whole available force in the body is undoubtedly due to oxidation. This oxidation is accomplished by means of the blood, and it is therefore evident that a continuous flow of oxygenated blood to the nerve centres is necessary as a source of power and of sensibility, as well as for the reintegration of nerve tissue. Any deficiency of oxygen in the blood is followed by a decreased arterialisation of the whole volume of the blood. Under these conditions the exhalation of carbonic acid is relatively less rapid than its formation, and life cannot continue if the blood in the arteries becomes thoroughly venous, as well in colour as in character. That nitrous oxide, when inhaled, changes the colour of the blood-corpuscles is evidenced by the livid appearance of the face and mucous surfaces; the latter, indeed, is a characteristic accompaniment of its administration, and the darkened colour of the blood may be observed as it flows from the severed vessels. This colour of the blood is probably in part due to uneliminated carbonic acid; but that nitrous oxide possesses in a high degree the property of darkening the blood-corpuscles may be easily demonstrated by directing a jet of the gas for a few seconds upon a little arterial blood in a test tube. Yet, from what has previously been advanced on this point, this latter result may more strictly be due to physical than to chemical causes. An interruption of the circulation in any part of the organism is soon followed by local insensibility in the tissues from which the blood supply may have been withdrawn; and it is beyond dispute that, during the anæsthetic state, the circulation of the blood through the capillary system becomes diminished in velocity. A tendency to stasis begins to appear, accompanied at the same time by a considerable reduction in the supply of arterial blood. These are facts that admit of experimental demonstration, as does also another fact, viz. that during the period of insensibility produced by the inhalation of nitrous oxide the brain itself is in a state of comparative anæmia. In short, it appears most probable that an arrest of the capillary circulation through the brain, to which several writers have attributed a potential influence as the cause of anæsthesia, is simply, so far as it may exist, a result of it.
The anæsthesia produced by the inhalation of nitrous oxide would, therefore, appear to be referable to an altered condition of the blood, whereby the molecular dynamic changes are interfered with, this interruption being probably due either to the retention of carbonic acid, or to the presence of nitrous oxide; or, as the result of both conditions, to the exclusion of oxygen.
For minor operations nitrous oxide possesses many advantages over other anæsthetics. The principal of these is its safety. In America, in 200,000 cases in which it had been administered, there was only one case of death. Furthermore its use is not contra-indicated in patients having any constitutional derangement, nor for women who are either pregnant or suckling.
Nitrogen, coal-gas, and carbonic acid have also been employed as anæsthetics.
The 'British Medical Journal' for June 13th, 1868, contains an account of some experiments performed by Dr Burdon Sanderson, at Middlesex Hospital, with nitrogen. It seems to have been longer in producing insensibility than nitrous oxide, but no lividity of countenance accompanied, nor sickness or headache followed, its administration.
=ANALEP'TIC.= _Syn._ ANALEP'TICUS, L.; ANALEPTIQUE, Fr. Restorative; that recruits the strength lost by sickness.
=Analep'tics.= _Syn._ ANALEP'TICA, L.; ANALEPTIQUES, Fr. In _pharmacology_, &c., restorative medicines and agents.
=ANAL'YSIS= (-e-s[)i]s). [Eng. L., Gr.] _Syn._ ANALYSE, Fr.; AUSLÖSUNG, ZERLEGUNG, Ger. In a gen. sense, the resolution of anything, whether an object of the senses or of the intellect, into its elementary parts. In _chemistry_, the resolution or separation of a compound body into its constituent parts or elements, for the purpose of either determining their nature, or, when this is known, their relative proportions. It is divided into QUAL'ITATIVE ANALYSIS and QUAN'TITATIVE ANALYSIS; and these again into PROX'IMATE ANALYSIS and UL'TIMATE ANALYSIS. The first consists in finding the components of a compound, merely as respects their nature or names; the second, in finding not merely the component parts, but also the proportions of each of them; the third gives the results in the names of the proximate or immediate principles or compounds which, by their union, form the body under examination; whilst the fourth develops the chemical elements of which it is composed.[56] An analysis may also be made to determine whether a certain body is or is not contained in a compound (as lead in wine); or it may be undertaken to ascertain all the constituents present; the extent of an investigation being merely limited by the object in view.
[Footnote 56: Thus, suet consists of olein, palmitin, and stearin. These would form the 'terms' of the PROXIMATE ANALYSIS of this substance. But olein, palmitin, and stearin consist of carbon, hydrogen, and oxygen. The ULTIMATE ANALYSIS of suet would, therefore, have reference to the elements carbon, hydrogen, and oxygen.]
For success in chemical analysis a thorough acquaintance with the various properties of bodies is required, as well as aptitude in applying this knowledge in discriminating them, and separating them from each other. Judgment and expertness in manipulation are, indeed, essential qualifications. The method pursued must likewise be such as to attain the object in view with unerring certainty, and in the most expeditious manner. "The mere knowledge of the reagents, and of the reactions of other bodies with them, will not suffice for the attainment of this end. This requires the additional knowledge of a systematic and progressive course of analysis, or, in other words, the knowledge of the order, and succession, in which solvents, together with general and special reagents, ought to be applied, both to effect the speedy and safe detection of every individual component of a compound or mixture, and to prove with certainty the absence of all other substances. If we do not possess this systematic knowledge, or if in the hope of attaining an object more rapidly, we adhere to no method in our investigations and experiments, analysing becomes (at least in the hands of a novice) mere guesswork, and the results obtained are no longer the fruits of scientific calculation, but mere matters of accident, which sometimes may prove lucky hits, and at others total failures." (Fresenius.)
=ANALYSIS, SPECTRUM.= More than half a century ago Sir John Herschel employed the prism in the analysis of coloured flames, and in 1834 Fox Talbot, by means of the same instrument, distinguished the difference between the spectra given by strontium and lithium, notwithstanding the similarity of the two in colour. But it was reserved for Messrs Kirchkoff and Bunsen, as the inventors of the spectroscope, to devise the only efficient method of analysing flame, and, at the same time, to furnish chemists with a means whereby they may detect with unerring certainty the presence of any known element by observing the spectrum it gives when such element is submitted to a temperature sufficiently high for it to emit a luminous vapour. That certain chemical substances when heated in the flame of the spirit-lamp or the blow-pipe, or any other source of comparatively white light, imparted characteristic colours to the flame, was a fact that had long been known to chemists; for example, when a salt of sodium was so treated, an intense yellow colour was imparted to the flame. A salt of potassium produced under the same circumstances a violet, strontium, a crimson colour, &c. These results could only be produced when the substance under examination contained but one of the salts in question. If more than one were present, this method of qualitative analysis was comparatively, if not wholly, valueless, because the specific colour communicated to the flame by the presence of one element would be masked, and, consequently, destroyed by the colour developed by the vapour of another or other elements. For instance, so much more vivid is the yellow colour given to flame by sodium salts than the violet tint imparted by those of potassium, that a very small trace of sodium prevents the unaided eye from perceiving the violet, even when the potassium compound is present in large quantity.