56 ANATOMY AND PHYSIOLOGY 



the oesophagus, as everything presented to them, 

 under circumstances of hunger, is swallowed with 

 ravenous avidity, without regard to quality or 

 flavor. 



SCHEME OF THE DISTRIBUTION OF THE VERTEBRAL NERVES 

 OF THE FISH, FOLLOWING THE COURSES OF THE FLOAT- 

 ING OR CILIARY BONES. 



AGE TO WHICH THEY LIVE. 



Perhaps there is no subject on which the natu- 

 ralist has labored with less success, than in trying 

 to ascertain the age to which fishes attain. Ad- 

 mitting that an individual of any species were un- 

 disturbed by enemies, or unmolested by its own 

 kindred, and quietly enjoying a circumscribed body 

 of water, amply supplied with appropriate food, 

 there is no reason for doubting that it would live 

 for many centuries. We know of no limits to 

 their longevity, nor can we suppose that the inter- 

 nal machinery would wear itself out, so long as 

 the digestive organs were properly excited. 



