162 THE LAWS OF ORGANIC 



important phenomena, and for this purpose shall 

 consider the three following subjects : 



1 . The nature and influence of those changes which pre- 



dispose to, or precede torpidity. 



2. The state of the system during the repose. 



3. The nature and influence of those changes which pre- 



dispose to, or precede the return to active life. 



CLXXIX. The period at which hibernating 

 animals undergo this extraordinary change is va- 

 rious in the different species, and even in those 

 of the same species. The greater number exhi- 

 bit a decline of the active powers of life, and re- 

 tire to their winter retreats in September and 

 October. At the latter end of autumn the 

 temperature of the atmosphere is much dimi- 

 nished, and at this season of the year cold and 

 bleak winds frequently occur, which tend still 

 more to affect the animal economy, 



CLXXX. I have endeavoured to shew that the 

 circulation of blood at different ages possesses differ- 

 ent characters, and, still further, that thegeneration 

 of animal heat in man is regulated by its various 

 conditions, and not by any power of the lungs in- 

 dependent of these conditions, or any power of the 

 nervous system, as universally supposed. Since the 

 correctness of this opinion cannot be doubted, we 

 have facts on the one hand, and probability on 

 the other, from analogy, to enforce the belief, 



