THEORIES OF HYBERNATION. 829 



and fishes than in mammalia, and least of all in 

 birds; while in hybernating animals it augments as 

 their respiration diminishes" 



In accordance with the foregoing strange and 

 unexplained doctrines, it is maintained by Dr. 

 W. F. Edwards, in his excellent work on the In- 

 fluence of Physical Agents on Life, translated 

 by Hodgkin and Fisher, that " the degree most 

 favourable to life is a cold temperature." (p. 89.) 

 And he adds in another Treatise, contained in 

 the Cyclopedia of Anatomy and Physiology, 

 that " in cold blooded animals, the vitality of 

 the nervous system is always greater than in such 

 as are warm blooded," that among reptiles and 

 fishes, " the maximum of vitality corresponds to 

 the depth of winter, and the minimum to the 

 height of summer." (vol. ii. p. 674.) 



Dr. Edwards seems to have arrived at these 

 conclusions, from finding that frogs, toads, and 

 salamanders, were capable of living longer under 

 aerated water reduced below the temperature of 

 50, than when at 100 and upwards : for ex- 

 ample, that when frogs were confined under water 

 of the Seine at 50, they lived from 5h. 50m. to 

 6h. 15m., and that when kept under water cooled 

 to 32, they lived from 6h. 7m. to 8h. & 18m. 

 But when the water was raised to the tempe- 

 rature of 72, (that of the air being 68,) they con- 

 tinued alive from 35m. to Ih. 10m. When raised 

 to 90, they died in from 12 to 32 minutes; and 



