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.
FIG. 1.--ATMOSPHERIC DUST.
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.
Fig. 2.--VARIOUS MICROBES. (Highly magnified.)
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.
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.