704 THE POPULAR SCIENCE MONTHLY. 



short exposure to heat the animal embryo is thus more easily killed 

 thau 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 interpreta- 

 tion 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 tempera- 

 ture 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 "be- 

 come 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 considera- 

 tions which led him to consider this view as more and more probable, 

 though none of them would be regarded as very relevant by physiolo- 

 gists of the present day. The space at my disposal will not permit 

 of my following him into these details — the reader curious on this sub- 

 ject must therefore consult Spallaozani's work for himself. 



The position of things about a century ago, therefore, was this : 

 Not a single living thing, ^%%^ or seed, had been shown to be able to 

 resist, when in the moist state, an exposure to boiling water for a sin- 

 gle 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 tem- 

 perature — 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 Kiihne, would seem to render this very 

 probable, and compel us to regard Spallanzani's experiments with seeds as needing repeti- 

 tion with the modification above suggested. The plants also, like the animals, should 

 have been wholly instead of partially immersed in the heated water. 



