Page:Popular Science Monthly Volume 5.djvu/723

Rh quickly dismisses, as even more improbable, the notion that the smallness of the germ or egg can act as its safeguard by rendering it less amenable to the influence of heat. Having thus cleared the ground, Spallanzani states what seems to him to be the principal reason of the difference observed. We ought to reflect, he says, upon the difference between the life of an animal in its egg stage and its subsequent life as a developed organism. For, however deficient our knowledge may be upon this subject, we may feel assured that life shows less of the characters of life in the egg than in the organism which is born from it. The life of the egg is "very feeble"—"its life has less of life." And then Spallanzani asks whether the fact of this life of the embryo within the egg being "so small and so feeble"—being "a life which deserves so little the name of life"—may not be the reason that eggs are able to bear the influence of heat better than the developed organisms whose life is more active and complex? He believes this to be the principal reason of the increased power of resisting heat displayed by eggs, and in support of it calls attention to the fact that many animals (as well as plants), when the rate of their vital phenomena is lowered, during winter sleep, are much better able to withstand many injurious external influences than when they are displaying to the full all the manifestations which constitute their "life." Animals, such as frogs and salamanders, for instance, live longer after and resist the effects of injuries better, when they have been incurred during the benumbing cold of winter rather than at periods when these organisms have been full of life and activity.

A similar difference obtains between the degree and complexity of the life of seeds as compared with that of plants, and this difference may in part similarly explain the superior power of resistance to heat shown by seeds—since here, also, among plants, we find that ability to withstand hurtful influences, generally, increases as their life becomes more sluggish. Thus Spallanzani says, "One may say that in winter plants live less fully than at other seasons, and during this period they are also much less liable to perish when they are plucked from the ground or unduly pruned, than if they had been treated in the same manner during summer."

Again, while a difference of the same kind may in part be cited as the cause of the less injurious effects of heat upon seeds and plants as compared with that which it exercises over eggs and animals respectively, Spallanzani points out that this difference between eggs and seeds is only in part due to the fact that the outer coats of most seeds are much harder than those of eggs, since the envelopes of some seeds which are only killed at a temperature near 212° are not harder than the shell of an egg which is nevertheless killed at the much lower temperature of 140° Fahr. This difference is explicable rather, according to Spallanzani, by the fact that the fluids contained within the egg are so much more abundant than those within the seed. In cases of