Page:Popular Science Monthly Volume 6.djvu/198

186 is altogether another question when we have to decide whether moist Bacteria or their germs are endowed with this seed-like property of developing after desiccation. To maintain his position, Spallanzani was compelled to assume that they did possess this potentiality. Modern science, however, on the basis of experiment, declares that they have no such property. We are told most unreservedly by Prof. Burdon-Sanderson, not only that "the germinal particles of microzyms (Bacteria) are rendered inactive by thorough drying without the application of heat," that is, by mere exposure to air for two or three days at a temperature of 104° Fahr., but also that, "fully-formed Bacteria are deprived of their power of further development by thorough desiccation." Thus is the most important assumption made by Spallanzani swept away, and with it all the strength that his position may have appeared to possess. Neither he, nor any of his followers, can hope to save their germs from the full action of heat by assuming the preëxistence of a protective desiccation, when they are told, on the unquestionable authority of Prof. Sanderson, that such desiccation would be in itself destructive to them.

We are left, therefore, now face to face with only one other question. Has the progress of science, it may be asked, since the time of Spallanzani, in any way tended to strengthen the possibility that Bacteria-germs or any forms of living matter in the moist state can resist the destructive action of boiling water, even for two or three minutes? And to this question a negative answer may be unreservedly given, since the progress of science has shown, on the contrary, that such a supposition becomes more and more improbable in the light of all uncomplicated investigations bearing on the subject. To these results of modern research I must now call the reader's attention.

In the first place, the specific question with which we are more immediately concerned, as to the thermal death-point of Bacteria and their germs, has itself been answered by most decisive experiments. As the writer has elsewhere already shown, all direct experimentation on this subject leads to the conclusion that Bacteria and their germs, whether visible or invisible, are killed by a brief exposure to a heat of 140° Fahr. in the moist state. Thus Dr. Sanderson's experiments having proved that the germs of these organisms are, as regards their ability to withstand desiccation, related to eggs rather than to seeds, the writer's own experiments tend to strengthen this resemblance by showing that these Bacteria-germs also (like the eggs with which Spallanzani experimented) are invariably killed at a temperature of about 140° Fahr.

Although, therefore, my experiments are not favorable to Spallanzani's assumptions, they are entirely in accordance with his experiments. The thermal death-point ascertained by him for the eggs of