CHYLIFICATION. 183 



however, is lower down, and especially at the part 

 where the tube, after having remained narrow in 

 the first half of its course, is dilated into a wider 

 cavity ; which is distinguished from the former by 

 the appellation of the great intestine, and which is 

 frequently more capacious than the stomach itself. 

 It is exceedingly probable that these two portions 

 of the canal perform different functions in refer- 

 ence to the assimilation of the food : but hitherto 

 no clue has been discovered to guide us through 

 the intricacies of this difficult part of physiology ; 

 and we can discern little more than the existence, 

 already mentioned, of a constant relation between 

 the nature of the aliment and the structure of the 

 intestines, which are longer, more tortuous, and 

 more complicated, and are furnished with more 

 extensive folds of the inner membrane, and with 

 larger and more numerous cteca, in animals that 

 feed on vegetable substances, than in carnivorous 

 animals of the same class. 



The class of /«5ec/5 supplies numberless examples 

 of the accurate adaptation of the structure of the 

 organs of assimilation to the nature of the food 

 which is to be converted into nutriment ; and also 

 of the general principle that vegetable aliment re- 

 quires, for this purpose, longer processes, and a 

 more complicated apparatus than that which has 

 been already animalized. In the herbivorous 

 tribes, we find the oesophagus either extremely 

 dilatable, so as to serve as a crop, or receptacle for 

 containing the food previously to its digestion, or 

 having a distinct pouch appended to it for the same 

 object : to this there generally succeeds a gizzard, 

 or apparatus for trituration, furnished, not merely 



