74 ANIMALCULA OF INFUSIONS. " I. 



nefs of food, or from inability to bear the winter, 

 or even a flight degree of cold. 



We have faid that Boerhaave thought 149^ 

 immediately killed certain birds and quadrupeds. 

 Surely 50° above blood heat is very great, and 

 cannot but be intolerable to many races of ani- 

 mals; yet we muft acknowledge it may be 

 borne, and that it is fo by many fpecies inhabiting 

 the torrid zone, and other very hot regions. And 

 it appears to me, that we fhould reafon on heat 

 which birds and the reft of animals can fupport 

 as we reafon on the cold. As thofe in the 

 northern climates can fuftain exceffive cold, fo 

 can thofe in the fouthern fuftain exceffive heat. 



It is eafy to afcertain the greateft cold that either 

 cetaceous or fquamous fi flies fuffer : it will al- 

 ways equal that of the water which they are in, 

 confequently in frefli water lefs than freezing, 

 elfe it would not continue fluid. Thofe inhabit- 

 ing fait waters, as the fea, will falfer a little 

 more. Thus fifhes are fecured againft the rigour 

 of cold to which innumerable animals are fo 

 much expofed. No lefs are they fheltered from 

 the burning heat of the atmofphere, excepting 

 thofe living in ihallow waters, and on that account 

 more or lefs fubjected to the influence of the 

 air from the predominating feafons or the climate. 

 From fome obfervations, we know there are 

 carp living in warm fprings that experience blood 



heat 



