90 



COMPARATIVE ZOOLOGY. 



hold about five pints; that of the Kangaroo is as long 

 as its body. 



The intestinal canal in Mammals begins at the pyloric 

 end of the stomach, where there is a kind of valve or cir- 

 cular muscle. Like the stomach, it varies greatly, accord- 

 ing to the nature of the food. It is generally longest in 

 the Vegetable-feeders, and shortest in the Flesh-feeders. 

 The greater length in the former is due to the fact that 

 vegetable food requires a longer 

 time for digestion, and that a great- 

 er bulk of such food is required to 

 obtain a given quantity of nutri- 

 ment. The intestines measure 150 

 feet in a full-grown Ox, while they 

 are but three times the length of 

 tlie body in the Lion, and six times 

 in Man. Save in some lower 

 forms, as the Whales, there are 

 two main divisions, the " small " 

 and " large " intestines, at the 

 junction of which is a valve. The 

 former is the longer of the two. 



ryjJ_j<o- ,fV/--.j'^pr« ^"^ ^° '^^ digestion is completed, 

 ^S^ ^-^Ji :; C-A% C^ I and from it the most of absorption 

 Fio. 58. -Section of the Wall of takes placc. Tiic large intestine is 



the Unmim Intestine (ifewm), . 



X 50: a, villi i 6 and d, glands; mainly a temporary lodging-place 



c and e, mucous membrane ; /, r.i i t. i^ ^t r -* 



circular muscles; 17, A, lougi- lor the uselcss part ot the food, 

 tndinai mnscies. ^^^^^ jj jg expelled from the body. 



The beginning of the small intestine is called the duode- 

 num, into which the ducts from tlie liver and pancreas 

 open. The intestinal canal has the same structure as the 

 stomach, and by a peristaltic motion its contents are pro- 

 pelled downward. The inside of the small intestine is 

 covered with a host of thread-like processes (mlli), resem- 

 bling the pile of velvet. 



