THERMAL DEATH-POINT OF LIVING MATTER, 703 



quickly dismisses, as even more improbable, the notion that the small- 

 ness 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 wliich 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 

 j^rincipal 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 benumb- 

 ing 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 be- 

 comes 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 respec- 

 tively, 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 tem- 

 perature of 1-40° 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 



