60 ON THE (ESOPHAGUS OF THE EUMINANTIA. 



During contraction, the points A and B, and also c and d, are 

 approximated. Bj the approximation of a to b the gullet 



is more rapidly shortened, and by the approximation of c to d 

 it is more rapidly constricted, than is the human gullet by the 

 action of the longitudinal and circular fibres ; and thereby a bolus 

 is carried more rapidly along the Euminant's gullet than along 

 Man's, or that of a Bird with its circular fibres only. This is a 

 great advantage in the case of the Euminant ; for the slow passage 

 of so much food backwards and forwards would very seriously 

 interfere with respiration by pressing upon the trachea. But, 

 on the other hand, why should the carnivorous animal have such 

 an oesophagus ? This fact renders necessary a second explana- 

 tion, viz. that hy this ^arrangement great strength is gained. The 

 same number of fibres as are present in the human gullet would 

 form a much stronger and more compact tube if interwoven in a 

 manner similar to that in the Euminant's oesophagus ; for the 

 fibres are so closely interlaced, that separation of them is ex- 

 tremely difficult ; while, in the human gullet, the fibres are more 

 apt to separate when pressing upon a hard bolus. And as the 

 muscular tunic of even the dog's and sheep's gullet is thicker than 

 that in the human subject, strength, in addition to rapidity of 

 transmission, is certainly gained. I have often been astonished 

 (before I knew the structure of its gullet) at the large masses of 

 unchewed food which a dog can readily swallow. 



1 have examined the sheep's oesophagus more especially ; for 

 that of the ox, though having the same structure, is much more 

 difficult to dissect on account of the greater brittleness of its 

 fibres when boiled. I have not examined the gullet of any other 

 Euminant, as I have been unable to procure any other. 



