Louis Olivier

“ But some of the germs may be obstinate or hardy, and we make a new trial, and for prudence a third and a fourth trial, after which we assume that all the bacteria have been destroyed. Unfortunately for the method of discontinuous heating, there are wary germs the development of which does not begin till after the fifth, the tenth, and even the twentieth day, and which, far from being stimulated in their growth by the successive heatings, at every repetition shut themselves up more closely in their latent seed-life. ”

“ Generally, these methods are founded on the fact that organic liquids become peopled with microphytes, or remain unchanged, according as the air comes to them charged with its normal quantity of germs, or after having been cleared of them by filtration. We can, therefore, examine the bacteria in the atmosphere by causing the air or the rain-water containing them to pass into liquors favorable to their nutrition, but previously free from them. Liquids for the culture of bacteria are easy to procure. ”

“ On the other hand, numerous tests have shown that dry dusts, especially those of hospitals, proceeding from substances in a state of putrefaction, sanious pus, and the dejections of the sick, are charged with microbes. Great agglomerations of men furnish the most of them. According to the measurements made in the Rue de Rivoli and Montsouris, the air in the interior of Paris is nine or ten times richer in bacteria than that in the neighborhood of the fortifications. At the observatory, the winds from the north bring many more than the winds from the south. ”

“ Storms in the pleasant season are followed by a growth of cryptogamic vegetation, and purify the atmosphere for only a very short time. Fifteen or eighteen hours after a rain, says M. Miquel, "the spores appear to be five or ten times as numerous as before. On the other hand, mineral dusts and several kinds of microbes continue to be rare till the moisture which has caused them to adhere to the blades of grass and the moist soil of the surface has dried away." ”

“ It is important to have the microbes collected in the broth of the tubes sown in different kinds of liquors. Such treatment furnishes the only means of discovering the nature of the organisms, for characteristics deduced from their shape are of no significance. Most frequently they can he distinguished only by the fermentations they produce. Numerous experiments based on this principle will be required for the exact determination of the bacteria in the atmosphere. ”

“ The continuation of the statistical researches that have been begun at Montsouris, and the microscopic analysis of the air and of water, particularly of sewer-water, cultivation, botanical and physiological investigation, and inoculation with the resultant germs, will certainly conduct to the solution of the problem. Then only, having become acquainted with our enemies, shall we be able to destroy them. The precautions that we take against such evasive foes—working as we do in the dark—by using antiseptics, are evidently insufficient. ”

“ A substance that kills one bacterium may not hinder the development of its neighbor, and our employment of antiseptics is always dependent upon their specific action. There exists no universal remedy against microbes. ”

“ It does not seem to be proved that the various spores introduced into our economy, to the number of 300,000 a day, or 100,000,000 a year, are perfectly innocuous. The appearance of thrush in the mouths of young children and in the respiratory canals of the dying seems to demonstrate also that the molds form a part of the class of parasites which are ready to take possession of our organism whenever it presents a vulnerable point or a point of weak resisting power. ”

“ A still more subtile cause of error must be guarded against. Cohn's mineral liquid will remain clear for an indefinite period after having been exposed to a heat of from 158° to 167°, without being free from germs; for, if we afterward add a quantity of broth which has been sterilized at 230°, the mixture of the two liquids, which, separate, would have continued perfectly limpid, will shortly swarm with bacilli and other organisms. Cohn's liquid can not be fully deprived of active germs till it has been boiled for four hours. If, continues M. Miquel ”

“ Among them are the mineral solutions of Pasteur and of Cohn, infusions of hay and of turnips, neutral urine, broths of chicken or beef, and Liebig's extract. It is, however, very hard to obtain such liquids absolutely pure of every living being. ”

“ Attention is, however, most strongly fixed upon the number and variety of spores of cryptogams of which the air operates as a vehicle of dissemination. Germs of the common molds, and the reproductive cells of the algae that live on the roofs of houses, on walls, and on damp earth, are nearly always abundant. ”

“ In studying under the microscope the development of these little organisms, in the preparations of which they have taken possession, a very curious evolution of one of the microbes of the air is revealed. The organism is a bacterium, which presents at first sight the characteristics of a very long, filamentous bacillus. M. Miquel affirms that he has seen this organism afterward divide itself into segments of unequal size, in such a way as to form strings of micrococci. The observation deserves consideration, for, if it is confirmed, and the ”

“ The vertical distribution of the microbes also shows that they come mostly from the dirt of our streets and houses. While a cubic metre of air at the top of the Pantheon contains only twenty-eight of them, the same quantity of air in the Park of Montsouris contains forty-five, and in the mairie of the fourth arrondissement, four hundred and sixty-two. ”

“ Fig. 3.—Spores of Algæ and Molds in the Atmosphere.
the development of molds is dependent upon both heat and moisture. The effect of moisture, however, varies according to the season, and with changes in temperature. Dry weather diminishes the number of germs in summer, and increases it in winter, while moist weather operates in an inverse manner. ”