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.[1]
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,
- ↑ Spallanzani's argument thus naturally suggests the notion that many of the seeds with which he experimented required a high temperature to kill them, merely on account of their dryness. If the seeds had been well soaked in cold water beforehand, so as to have thoroughly moistened them, might they not have been killed at a much lower temperature—that is, only a little, if at all, above 140° Fahr., or the temperature which proved destructive to the more moist animal germs? Facts which will be subsequently mentioned, since ascertained by Max Schultze and Kühne, would seem to render this very probable, and compel us to regard Spallanzani's experiments with seeds as needing repetition with the modification above suggested. The plants also, like the animals, should have been wholly instead of partially immersed in the heated water.
