50 PHYSIOLOGY OP THE EGGS 



what can be resisted by their eggs. What can be 

 the cause of this great difference ? Insects killed 

 at sixteen and fourteen degrees, are so completely 

 penetrated and frozen, that their members do not 

 yield to the pressure of the finger, and even under 

 the knife they appear perfect ice. This is not the 

 case with eggs ; for the contents of the shell, or 

 crust, remain as fluid under the influence of the 

 greatest cold, which can be ascertained by squeezing 

 them with the nail of the finger. This may arise 

 from their constituent parts being oleaginous or 

 spirituous, or from some inherent principle adapted 

 to resist the power of cold." 



We are not at all enlightened by what Spallanzani 

 has offered as a cause why eggs are enabled to resist 

 the effects of cold, as he has given us no satisfactory 

 explanation of the phenomenon. 



He proceeds, " If eggs do not freeze, it is probable 

 that the included embryoes do not freeze. Is there 

 any thing surprising, therefore, that they are capable 

 of resisting that cold which proves fatal to their 

 contained insect when produced ? Perhaps, for the 

 same reason, (and I can perceive no applicable 

 objection,) animalcula concentrated, or in the germ, 

 can support a degree of cold which they are incapable 

 of enduring when emerged. 



" It may be asked, as the temperature of freezing 

 still retains a portion of heat, why should it not 

 develope the germs of the most minute animalcula ? 

 If we had never seen any eggs hatched but those of 

 birds, which require a hundred and four degrees, 



