Chapter 10

The brook near where my observations were made was fast decreasing in volume, and would probably continue to do so until in July its bed would be nearly dry. During the wet seasons the meadow is itself covered. Even in the banks of the stream, then under water, there were holes, but they all extended obliquely without exception, there being no perpendicular burrows and no mounds. The holes extended in about six inches, and there was never a perpendicular branch, nor even an enlargement at the end. I always found the inhabitant near the mouth, and by quickly cutting off the rear part of the hole could force him out, but unless forcibly driven out it would never leave the hole, not even when a stick was thrust in behind it. It was undoubtedly this species that Dr. Godman mentioned in his "Rambles of a Naturalist," and which Dr. Abbott _(Am. Nal.,_ 1873, p. 81) refers to _C. bartonii_. Although I have no proof that this is so, I am inclined to believe that the burrowing crayfishes retire to the stream in winter and remain there until early spring, when they construct their burrows for the purpose of rearing their young and escaping the summer droughts. My reason for saying this is that I found one burrow which on my first visit was but six inches deep, and later had been projected to a depth at least twice as great, and the inhabitant was an old female.

I think that after the winter has passed, and while the marsh is still covered with water, impregnation takes place and burrows are immediately begun. I do not believe that the same burrow is occupied for more than one year, as it would probably fill up during the winter. At first it burrows diagonally, and as long as the mouth is covered with water is satisfied with this oblique hole. When the water recedes, leaving the opening uncovered, the burrow must be dug deeper, and the economy of a perpendicular burrow must immediately suggest itself. From that time the perpendicular direction is preserved with more or less regularity. Immediately after the perpendicular hole is begun, a shorter opening to the surface is needed for conveying the mud from the nest, and then the perpendicular opening is made. Mud from this, and also from the first part of the perpendicular burrow, is carried out of the diagonal opening and deposited on the edge. If a freshet occurs before this rim of mud has had a chance to harden, it is washed away, and no mound is formed over the oblique burrow.

After the vertical opening is made, as the hole is bored deeper, mud is deposited on the edge, and the deeper it is dug the higher the mound. I do not think that the chimney is a necessary part of the nest, but simply the result of digging. I carried away several mounds, and in a week revisited the place, and no attempt had been made to replace them; but in one case, where I had in addition partly destroyed the burrow by dropping mud into it, there was a simple half rim of mud around the edge, showing that the crayfish had been at work; and as the mud was dry the clearing must have been done soon after my departure. That the crayfish retreats as the water in the ground falls lower and lower is proved by the fact that at various intervals there are bottled-shaped cavities marking the end of the burrow at an earlier period. A few of those mounds farthest from the stream had their mouths closed by a pellet of mud. It is said that all are closed during the summer months.

How these animals can live for months in the muddy, impure water is to me a puzzle. They are very sluggish, possessing none of the quick motions of their allied _C. bartonii,_ for when taken out and placed either in water or on the ground, they move very slowly. The power of throwing off their claws when these are grasped is often exercised. About the middle of May the eggs hatch, and for a time the young cling to the mother, but I am unable to state how long they remain thus. After hatching they must grow rapidly, and soon the burrow will be too small for them to live in, and they must migrate. It would be interesting to know more about the habits of this peculiar species, about which so little has been written. An interesting point to settle would be how and where it gets its food. The burrow contains none, either animal or vegetable. Food must be procured at night, or when the sun is not shining brightly. In the spring and fall the green stalks of meadow grasses would furnish food, but when these become parched and dry they must either dig after and eat the roots, or search in the stream. I feel satisfied that they do not tunnel among the roots, for if they did so these burrows would be frequently met with. Little has as yet been published upon this subject, and that little covers only two spring months--April and May--and it would be interesting if those who have an opportunity to watch the species during other seasons, or who have observed them at any season of the year, would make known their results.

RALPH S. TARR

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OUR SERVANTS, THE MICROBES.

Who of us has not, in a partially darkened room, seen the rays of the sun, as they entered through apertures or chinks in the shutters, exhibit their track by lighting up the infinitely small corpuscles contained in the air? Such corpuscles always exist, except in the atmosphere of lofty mountains, and they constitute the dust of the air. A microscopic examination of them is a matter of curiosity. Each flock is a true museum (Fig. 1), wherein we find grains of mineral substances associated with organic debris, and germs of living organisms, among which must be mentioned the _microbes_.

Since the splendid researches of Mr. Pasteur and his pupils on fermentation and contagious diseases, the question of microbes has become the order of the day.

In order to show our readers the importance of the study of the microbes, and the results that may be reached by following the scientific method created by Mr. Pasteur, it appears to us indispensable to give a summary of the history of these organisms. In the first place, what is a microbe? Although much employed, the word has not been well defined, and it would be easy to find several definitions of it. In its most general sense, the term microbe designates certain colorless algæ belonging to the family Bacteriaceæ, the principal forms of which are known under the name of _Micrococcus. Bacterium, Bacillus. Vibrio, /Spirillum, etc_.

In order to observe these different forms of Bacteriaceæ it is only necessary to examine microscopically a drop of water in which organic matter has been macerated, when there will be seen _Micrococci_ (Fig. 2, I.)looking like spherical granules, _Bacteria_ in the form of very short rods, _Bacilli_ (Fig. 2, V.), _Vibriones_ (Fig. 2, IV.,) moving their straight or curved filaments, and _Spirilli_ (Fig. 2, VI.), rolled up spirally. These varied forms are not absolutely constant, for it often happens in the course of its existence that a species assumes different shapes, so that it is difficult to take the form of these algæ as a basis for classifying them, when all the phases of their development have not been studied.

The Bacteriaceæ are reproduced with amazing rapidity. If the temperature is proper, a limpid liquid such as chicken or veal broth will, in a few hours, become turbid and contain millions of these organisms. Multiplication is effected through fission, that is to say, each globule or filament, after elongating, divides into two segments, each of which increases in its turn, to again divide into two parts, and so on (Fig. 2, I. b). But multiplication in this way only takes place when the bacteria are placed in a proper nutritive liquid; and it ceases when the liquid becomes impoverished and the conditions of life become difficult. It is at this moment that the formation of _spores_ occurs--reproductive bodies that are destined to permit the algæ to traverse, without perishing, those phases where life is impossible. The spores are small, brilliant bodies that form in the center or at the extremity of each articulation or globule of the bacterium (Fig. 2, II. l), and are set free through the breaking up of the joints. There are, therefore, two phases to be distinguished in the life of microbes--that of active life, during which they multiply with great rapidity, are most active, and cause sicknesses or fermentations, and that of retarded life, that is to say, the state, of resting spores in which the organisms are inactive and consequently harmless. It is curious to find that the resistance to the two causes of destruction is very different in the two cases.

In the state of active life the bacterides are killed by a temperature of from 70 to 80 degrees, while the spores require the application of a temperature of from 100 to 120 degrees to kill them. Oxygen of a high pressure, which is, as well known from Bert's researches, a poison for living beings, kills many bacteria in the state of active life, but has no influence upon their spores.

In a state of active life the bacteriae are interesting to study. The absence of green matter prevents them from feeding upon mineral matter, and they are therefore obliged to subsist upon organic matter, just as do plants that are destitute of chlorophyl (such as fungi, broomrapes, etc.). This is why they are only met with in living beings or upon organic substances. The majority of these algae develop very well in the air, and then consume oxygen and exhale carbonic acid, like all living beings. If the supply of air be cut off, they resist asphyxia and take the oxygen that they require from the compounds that surround them. The result is a complete and rapid decomposition of the organic materials, or a fermentation. Finally, there are even certain species that die in the presence of free oxygen, and that can only live by protecting themselves from contact with this gas through a sort of jelly. These are ferments, such as _Bacillus amylobacter,_ or butyric ferment, and _B. septicus_, or ferment of the putrefaction of nitrogenized substances.

These properties explain the regular distribution of bacteria in liquids exposed to the air. Thus, in water in which plants have been macerated the surface of the liquid is occupied by _Bacillus subtilis_. which has need of free oxygen in order to live, while in the bulk of the liquid, in the vegetable tissues, we find other bacteria, notably _B. amylobacter_, which lives very well by consuming oxygen in a state of combination. Bacteria, then, can only live in organic matters, now in the presence and now in the absence of air.

What we have just said allows us to understand the process of cultivating these organisms. When it is desired to obtain these algae, we must take organic matters or infusions of such. These liquids or substances are heated to at least 120° in order to kill the germs that they may contain, and this is called "sterilizing." In this sterilized liquid are then sown the bacteria that it is desired to study, and by this means they can be obtained in a state of very great purity.

The Bacteriaceae are very numerous. Among them we must distinguish those that live in inert organic matters, alimentary substances, or debris of living beings, and which cause chemical decompositions called fermentations. Such are _Mycoderma aceti_, which converts the alcohol of fermented beverages into vinegar; _Micrococcus ureae_, which converts the urea of urine into carbonate of ammonia, and _Micrococcus nitrificans,_ which converts nitrogenized matters into intrates, etc. Some, that live upon food products, produce therein special coloring matters; such are the bacterium of blue milk, and _Micrococcus prodigiosus_ (Fig. 2, I.), a red alga that lives upon bread and forms those bloody spots that were formerly considered by the superstitious as the precursors of great calamities.

Another group of bacteria has assumed considerable importance in pathology, and that is the one whose species inhabit the tissues of living animals, and cause more or less serious alterations therein, and often death. Most contagious diseases and epidemics are due to algæ of this latter group. To cite only those whose origin is well known, we may mention the bacterium that causes charbon, the micrococcus of chicken cholera, and that of hog measles.

It will be seen from this sketch how important the study of these organisms is to man, since be must defend his body against their invasions or utilize them for bringing about useful chemical modifications in organic matters.

_Our Servants._--We scarcely know what services microbes may render us, yet the study of them, which has but recently been begun, has already shown, through the remarkable labors of Messrs. Pasteur, Schloesing and Muntz, Van Tieghem, Cohn, Koch, etc., the importance of these organisms in nature. All of us have seen wine when exposed to air gradually sour, and become converted into vinegar, and we know that in this case the surface of the liquid is covered with white pellicles called "mother of vinegar." These pellicles are made up of myriads of globules of _Mycoderma aceti_. This mycoderm is the principal agent in the acidification of wine, and it is it that takes oxygen from the air and fixes it in the alcohol to convert it into vinegar. If the pellicle that forms becomes immersed in the liquid, the wine will cease to sour.

The vinegar manufacturers of Orleans did not suspect the role of the mother of vinegar in the production of this article when they were employing empirical processes that had been established by practice. The vats were often infested by small worms ("vinegar eals") which disputed with the mycoderma for the oxygen, killed it through submersion, and caused the loss of batches that had been under troublesome preparation for months. Since Mr. Pasteur's researches, the _Mycoderma aceti_ has been sown directly in the slightly acidified wine, and an excellent quality of vinegar has thus been obtained, with no fear of an occurrence of the disasters that accompanied the old process.

Another example will show us the microbes in activity in the earth. Let us take a pinch of vegetable mould, water it with ammonia compounds, and analyze it, and we shall find nitrates therein. Whence came these nitrates? They came from the oxidation of the ammonia compounds brought about by moistening, since the nitrogen of the air does not seem to combine under normal conditions with the surrounding oxygen. This oxidation of ammonia compounds is brought about, as has been shown by Messrs. Schloesing and Muntz, by a special ferment, the _Micrococcus nitrificans_, that belongs to the group of Bacteriacæ. In fact, the vapors of chloroform, which anesthetize plants, also prevent nitrification, since they anaesthetize the nitric ferment. So, too, when we heat vegetable humus to 100°, nitrification is arrested, because the ferment is killed. Finally, we may sow the nitric ferment in calcined earth and cause nitrification to occur therein as surely as we can bring about a fermentation in wine by sowing _Mycoderma aceti_ in it.

The nitric ferment exists in all soils and in all latitudes, and converts the ammoniacal matters carried along by the rain into nitrates of a form most assimilable by plants. It therefore constitutes one of the important elements for fertilizing the earth.

Finally, we must refer to the numerous bacteria that occasion putrefaction in vegetable or animal organisms. These microbes, which float in the air, fall upon dead animals or plants, develop thereon, and convert into mineral matters the immediate principles of which the tissues are composed, and thus continually restore to the air and soil the elements necessary for the formation of new organic substances. Thus, _Bacillus amylobacter_ (Fig. 2, II.), as Mr. Van Tieghem has shown, subsists upon the hydrocarbons contained in plants, and disorganizes vegetable tissues in disengaging hydrogen, carbonic acid, and vegetable acids. _Bacterium roseopersicina_ forms, in pools, rosy or red pellicles that cover vegetable debris and disengage gases of an offensive odor. This bacterium develops in so great quantity upon low shores covered with fragments of algæ as to sometimes spread over an extent of several kilometers. These microbes, like many others, continuously mineralize organic substances, and thus exhibit themselves as the indispensable agents of the movement of the matter that incessantly circulates from the mineral to the organic world, and _vice versa_.--_Science et Nature._

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Palms sprouted from seeds kept warm by contact of the vessel with the water boiler of a kitchen range are grown by a man in New York.

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EPITAPHIUM CHYMICUM.

The following epitaph was written by a Dr. Godfrey, who died in Dublin in 1755:

Here lieth, to _digest macerate_, and _amalgamate_ into clay, _In Batneo Arenæ_, _Stratum super Stratum_ The _Residuum, Terra damnata_ and _Caput Mortuum_, Of BOYLE GODFREY, Chymist and M.D. A man who in this Earthly Laboratory pursued various _Processes_ to obtain _Arcanum Vitæ_, Or the Secret to Live; Also _Aurum Vitæ_, or the art of getting rather than making gold. _Alchymist_-like, all his Labour and _Projection_, as _Mercury_ in the Fire, _Evaporated_ in _Fume_ when he _Dissolved_ to his first principles. He _departed_ as poor as the last drops of an _Alembic_; for Riches are not poured on the _Adepts_ of this world. Though fond of News, he carefully avoided the _Fermentation, Effervescence_, and _Decrepitation_ of this life. Full seventy years his _Exalted Essence_ was _hermetically_ sealed in its _Terrene Matrass_; but the Radical Moisture being _exhausted_, the _Elixir Vitæ_ spent, And _exsiccate_ to a _Cuticle_, he could not _suspend_ longer in his _Vehicle_, but _precipitated Gradatim, per_ _Campanam_, to his original dust. May that light, brighter than _Bolognian Phosphorus_, Preserve him from the _Athanor, Empyreuma_, and _Reverberatory Furnace_ of the other world, Depurate him from the _Fæces_ and _Scoria_ of this, Highly _Rectify_ and _Volatilize_, his _æthereal_ spirit, Bring it over the _Helm_ of the _Retort_ of this Globe, place in a proper _Recipient_ or _Crystalline_ orb, Among the elect of the _Flowers of Benjamin_; never to be _saturated_ till the General _Resuscitation, Deflagration, Calcination,_ and _Sublimation_ of all things.

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A NEW STOVE CLIMBER.

(_Ipomæa thomsoniana_.)

The first time we saw flowers of this beautiful new climbing plant (about a year ago) we thought that it was a white-flowered variety of the favorite old Ipomæa Horsfalliæ, as it so nearly resembles it. It has, however, been proved to be a distinct new species, and Dr. Masters has named it in compliment to Mr. Thomson of Edinburgh. It differs from I. Horsfalliæ in having the leaflets in sets of threes instead of fives, and, moreover, they are quite entire. The flowers, too, are quite double the size of those of Horsfalliæ, but are produced in clusters in much the same way; they are snow-white. This Ipomæa is indeed a welcome addition to the list of stove-climbing plants, and will undoubtedly become as popular as I. Horsfalliæ, which may be found in almost every stove. It is of easy culture and of rapid growth, and it is to be hoped that it is as continuous in flowering as Horsfalliæ. It is among the new plants of the year now being distributed by Mr. B.S. Williams, of the Victoria Nurseries, Upper Holloway.--_The Garden_.

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HISTORY OF WHEAT.

Isis was supposed to have introduced wheat into Egypt, Demeter into Greece, and the Emperor Chin-Wong into China, about 3000 B.C. In Europe it was cultivated before the period of history, as samples have been recovered from the lacustrine dwellings of Switzerland.

The first wheat raised in the "New World" was sown by the Spaniards on the island of Isabella, in January, 1494, and on March the 30th the ears were gathered. The foundation of the wheat harvest of Mexico is said to have been three or four grains carefully cultivated in 1530, and preserved by a slave of Cortez. The first crop of Quito was raised by a Franciscan monk in front of the convent. Garcilasso de la Vega affirms that in Peru, up to 1658, wheaten bread had not been sold in Cusco. Wheat was first sown by Goshnold Cuttyhunk, on one of the Elizabeth Islands in Buzzard's Bay, off Massachusetts, in 1602, when he first explored the coast. In 1604, on the island of St. Croix, near Calais, Me., the Sieur de Monts had some wheat sown which flourished finely. In 1611 the first wheat appears to have been sown in Virginia. In 1626, samples of wheat grown in the Dutch Colony at New Netherlands were shown in Holland. It is probable that wheat was sown in the Plymouth Colony prior to 1629, though we find no record of it, and in 1629 wheat was ordered from England to be used as seed. In 1718 wheat was introduced into the valley of the Mississippi by the "Western Company." In 1799 it was among the cultivated crops of the Pimos Indians of the Gila River, New Mexico.

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DETERMINATION OF STARCH.

According to Bunzener and Fries _(Zeitschrift fur das gesammte Brauwesen_), a thick, sirupy starch paste prepared with a boiling one per cent solution of salicylic acid is only very slowly saccharified, and on cooling deposits crystalline plates of starch. For the determination of starch in barley the finely-ground sample is boiled for three-quarters of an hour with about thirty times its weight of a one per cent solution of salicylic acid, the resulting colorless opalescent liquid filtered with the aid of suction, and the starch therein inverted by means of hydrochloric acid. The dextrose formed is estimated by Fehling's solution. The results are one to two per cent higher than when the starch is brought into solution by water at 135° C.

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