Page:Popular Science Monthly Volume 5.djvu/724

704 short exposure to heat the animal embryo is thus more easily killed than the vegetable embryo, because its greater moisture causes it rapidly to experience the full effect of the heat, which the seed may possibly escape.

Now, then, for the application of the facts, toward the interpretation of Spallanzani's other experiments in which the lowest organisms appeared in closed flasks whose contents had been exposed to the temperature of boiling water for half an hour. Certainly the germs of such animalcules could not be supposed to have survived such an ordeal if they are to be compared with the eggs of animals, whose death has been brought about by momentary exposure to a temperature far short of the boiling-point. The supposition would, however, seem more possible, if, instead of comparing these germs with the eggs of animals, one regarded them as belonging to the same category as the seeds of plants. Spallanzani frankly admits that they would seem to be more allied to eggs than to seeds, though he attempts to bridge the gap by saying that certain eggs are known (to which these germs may be allied), in some respects resembling seeds. Such eggs "become dry, are preserved in this state, and then develop like seeds after they have been placed in some damp medium.... Why, then," he adds, "may not the germs of the lowest kind of animalcules be possessed of a similar nature?" He next (pp. 69-73) adduces various considerations which led him to consider this view as more and more probable, though none of them would be regarded as very relevant by physiologists of the present day. The space at my disposal will not permit of my following him into these details––the reader curious on this subject must therefore consult Spallanzani's work for himself.

The posítion of things about a century ago, therefore, was this: Not a single living thing, egg, or seed, had been shown to be able to resist, when in the moist state, an exposure to boiling water for a single moment. All naturally moist forms of living matter with which experiment had been made had been shown to be killed by a much lower heat, that is, at a temperature of about 140° Fahr., or less. And, in order to account for the appearance of the lowest animalcules in previously-boiled fluids, Spallanzani assumed—1. That these unknown germs were of the nature of seeds rather than eggs—seeing that they were capable (as he supposed) of undergoing desiccation with impunity,