Jean Henri Fabre

Germs

"W HEN a sunbeam penetrates the twilight of a darkened room its course is defined by a straight shaft in which innumerable corpuscles, rendered visible by the bright illumination, are seen whirling and eddying in constant though gentle motion. Outside of this shaft the air, though it appears to us perfectly limpid, is laden in the same degree with similar particles of dust. On account of their smallness these atmospheric impurities escape detection; but let a ray of sunshine illuminate them and turn each one into a point of light, and straightway they become visible, at any rate the largest ones. Others, and these form the greater number, defy the scrutiny of the sharpest eye even in a ray of light.

"Now, what are these atoms, visible and invisible? They are made up of an inextricable mixture of a little of everything. There are mineral particles raised from the ground by the wind, coal-dust from the smoke emitted by our stoves and fireplaces, tiny shreds of wool and cotton worn away by the friction of our clothes, minute fragments of wood from the wainscoting, and loosened particles of paint. In short, the pulverized product of all the wear and tear that goes on around us is here represented.

"So far there is nothing remarkable and certainly nothing dangerous unless in exceptional circumstances, when this atmospheric dust comes from poisonous substances. Our interest in the subject increases when we learn that there also float in the air, in prodigious multitudes, all sorts of germs of animalcules, seeds of the lowest forms of vegetable life, in most instances too small to be seen without the aid of a good microscope.

"Let us consider the simplest case, that of mold. Every one knows that a slice of any fruit, a melon for example, if left exposed to the air, no sooner decays than it is covered with a long silky down. This down, composed of ramified filaments standing up against one another, is a vegetable growth belonging to the same class as the mushroom. Its common name is mold. Whence comes this plant, so curious if examined closely, with its little black heads full of spores? Is it engendered by decay?

"That is the general belief; but let us not be deceived. Decay does not engender anything; it is not a cause but a result. The slice of melon in decaying does not create the mold; on the contrary, it is the mold that induces the decay of the slice of melon, at the expense of which it develops. This lowest form of vegetable life has its origin in a germ, we may call it a seed, just as an oak has its origin in an acorn. Every living thing, animal or plant, without any exception, is derived from a previous living thing of like sort, which has furnished the germ or seed for the new life. Life is always the product of life, never of decay.

"Accordingly, the mold must have been sown. But by whom or what? Evidently by the air, for air is the only thing that has come in contact with the slice of melon. The conclusion is obvious: there are in the air, floating unseen amid the multitude of other microscopic particles, the germs of mold that induce the rotting of fruit; they are there in immense numbers, for the growth of mold is very thick; they are everywhere, for in whatever part of the house the slice of melon is left, it is attacked by mold; and, finally, there are many different kinds, each one attacking the vegetable or animal substance it likes best.

"These germs come from former molds whose invisible and innumerable seeds were thrown into the air by the bursting open of the ripened fruit of the mold. Almost without weight, and wafted this way and that by the slightest current of air, they sooner or later fall upon some body favorable to their germination, a slice of melon or something else. The sowing is accomplished and the plant grows.

"Held in the air and borne hither and thither by it are similar multitudes of germs representing organisms known as animalcules, infinite in variety, and all too minute to be seen without the aid of a microscope. These animalcules are called infusoria because the simplest way to obtain them is to infuse in water any substance, animal or vegetable. Let us put to soak in a little water a few pinches of hay chopped up fine, or some bits of grass, no matter which. In a few days, especially in the heat of summer, the most curious population will be found swarming in the liquid. A drop of this water no bigger than a pin's head shows us under the powerful eye of the microscope a startling spectacle. In the ocean of this drop confined between two thin plates of glass, there come and go, swim and plunge and rise again by the aid of their cilia, infusoria of many varieties, all in unceasing motion. Some are flattened and oval in shape, somewhat resembling a certain sea-fish, the sole; others are bristling globules, whirling rapidly; still others, attached to some bit of foliage by a spiral thread, present from above the shape of a bell, the mouth of which, fringed with cilia in rapid vibration, gives the appearance of a wheel revolving swiftly. Then suddenly the spiral thread tightens, the opening of the bell closes, the cilia cease to vibrate. A tiny prey has just been caught and the infusorium contracts to digest its victim at leisure.

"Let us pause here in our description of these animalcules and turn our attention to the origin of the infusoria.

"This aquatic population having its home in water in which grass or other organic matter has decayed can come only from germs brought by the air. Let us boil a little hay in water and pour the still hot and limpid decoction into a glass. The liquid, when freed from the last remnants of hay, is perfectly clear, with a slightly yellowish tinge. But, behold, in a few days it becomes clouded, turbid. Examined closely under a microscope, it is seen to be peopled with infusoria. The germs of these animalcules were not furnished by the water and hay used, for if they contained any, which might well have been the case, the act of boiling would have killed them beyond resuscitation. Let us bear this fact well in mind, as we shall soon find important applications of it; no live thing, even if it be in the form of a germ, can withstand the temperature of boiling water. Plant, animal, egg, germ, seed, all perish in the heat required for raising water to the boiling point. Our boiling-hot decoction, therefore, did not contain anything having life. If, then, a few days after cooling off, it is found to be teeming with life, these organisms can owe their origin only to the dust of the air, rich in infusorial germs.

"Should any doubts remain on this point, the following experiment will dispel them. The infusion is poured into a glass flask, the neck of which is then melted and drawn out into a fine tube. The liquid is now raised to the boiling point in the body of the flask. Steam rises and as it escapes in a jet through the small opening of the extended neck it drives out all the air, after which the flask is hermetically sealed by melting the tip of the neck. Henceforth no infusoria can by any possibility make their appearance. For years and years the decoction of hay will remain perfectly limpid, developing not the slightest cloudiness, and microscopic examination will prove that the clear liquid contains nothing capable of producing life without intervention from outside. But let the tip of the neck be broken and air enter, and very soon the usual infusoria will appear.

"Below the infusoria are microbes, smaller in size, of much simpler structure, and apparently belonging to the vegetable kingdom. Microbes are the infinitely small in living form. A thousand of them placed end to end would in most instances measure scarcely a millimeter. There are some that are visible only under the most powerful microscope. Thus examined, they appear as bright points, constantly trembling and of various shapes, some oval or rounded, others rod-shaped, and still others bent or curved like a comma. They are everywhere, in numbers that defy counting; they are in the air, the water, the ground, in decaying matter, in the bodies of animals, and in our own bodies. They lay claim to everything.

Microbes (much enlarged)

"What part do these infinitesimal organisms play in the order of things? They play a very important one. Let us give two examples.

"An animal dies. Its body decays and is soon resolved into its primitive elements, which are seized upon for the nourishment of growing vegetation. The putrefying flesh is converted into flower, fruit, grain, nutritive matter. What agency effects this wonderful transformation? It is the microbe, which clears away dead matter and restores its elements to the realm of the living. By developing and multiplying they induce decay, which gives back to life's workshop materials otherwise unavailable for use. Without their intervention the work of life would be impossible because the work of death would be incomplete.

"As another instance take grape juice in the process of fermenting and becoming wine. The liquid heats as the result of its own internal activity; it begins to foam, and big bubbles of carbonic acid gas are formed, until at last there is developed that winy flavor which succeeds to the sugary taste of the earlier stages. This process is called fermentation. What induces it and thus gives us wine? It is a microbe, the same as that we find in yeast. In order to get nourishment for itself and to multiply until its numbers defy computation, this yeast microbe decomposes the sugar in the grape juice, resolving it into alcohol, which remains in the liquid, and carbonic acid gas, which escapes. Such is the secret of the making of wine, beer, and other fermented drinks.

"Among the various tasks performed by microbes let us henceforth remember putrefaction and fermentation.

"These two infinitely small destroyers, one of which makes alcohol out of sugar, and the other reduces a dead body to dust and gas, warn us that other microbes carrying on their work of demolition at the expense of our own organs may by their prodigious multitude give rise to dangerous diseases. One of them, in fact, produces cholera, that terrible epidemic the very name of which terrifies us; another causes typhoid fever, which every year claims thousands of victims; and still others, each according to its aptitude, engender various ills which science is every day making known to us in increasing numbers. The decay of our teeth, with the extreme pain caused by it, is due to a microbe; the slow wasting away of a consumptive's lungs is traced to a microbe; the big purple carbuncle that causes so much suffering, this too is the work of a microbe. Enough of these tortures for the present. You can see that of all our enemies the infinitely small is the most terrible.

"Microbes are everywhere, we say, especially where filthy conditions prevail, whether in the air or in the water. The air in a hospital ward contains more microbes than that outside; the air of cities, where we lived piled one on another, so to speak, has far more than the air of the country; the air of low plains carries a greater number than that of the uplands. High mountain air has none at all. There in truth may be found the pure atmosphere so conducive to health.

"Water is even richer than air in microbes, especially when it is defiled with sewage. It is estimated that such water may contain various kinds of microbes and their germs to the frightful number of one hundred million per liter. Not all of these, it is safe to say, are harmful; far from it; but in so immense a multitude there must certainly be some bad ones."