DEGLUTITION. 177 



oesophagus is a very wide canal, admitting of 

 great dilatation. This is the case with many 

 carnivorous birds, especially those that feed on 

 fishes, where its great capacity enables it to 

 hold, for a considerable time, the large fish which 

 are swallowed entire, and which could not con- 

 veniently be admitted into the stomach. Blu- 

 menbach relates that a sea-gull, which he kept 

 alive for many years, could swallow bones of 

 three or four inches in length, so that only 

 their lower ends reached the stomach, and were 

 digested, w hile their upper ends projected into 

 the oesophagus, and descended gradually in 

 proportion as the former were dissolved. Ser- 

 pents, w hich swallow animals larger than them- 

 selves, have, of course, the oesophagus, as well 

 as the throat, capable of great dilatation ; and 

 the food occupies a long time in passing through 

 it, before it reaches the digesting cavity. The 

 turtle has also a capacious oesophagus, the inner 

 coat of which is beset with numerous firm and 

 sharp processes, having their points directed 

 towards the stomach ; these are evidently in- 

 tended to prevent the return of the food into the 

 mouth. Grazing quadrupeds, who, while they 

 eat, carry their heads close to the ground, have 

 a long oesophagus, with thick muscular coats, 

 capable of exerting considerable power in pro- 

 pelling the food in the direction of the stomach, 

 which is contrary to that of gi'avity. 



VOL. II. N 



