CHAPTER I. Ill 

 THE MECHANISMS OF DIGESTION Coi t'd 



THE MOVEMENTS OF THE INTESTINES 



The length of the small intestine and the size of the cecum • 

 large intestine vary considerably in differenl animal-. In r 

 such as the cat, the small intestine is relatively short; in tl 

 relatively long. Thus, it is three times the Length of the body in tl 

 and four to six times in the dog; whereas in the goal and - 

 be nearly thirty times the Length of the body. In the carnivora 

 cecum is either absent or rudimentary, whereas in those herbivora wh 

 do not have a divided stomach the cecum is very Large an 

 as is also the colon. The reason for the greal size in h< hat 



practically the whole of the digestion of cellulose takes place in this 

 part of the gut. This digestion, as we shall see 



on any secretion poured forth by the animal itself, but upon I ion 



of bacteria and of certain enzymes (cytt 3ea thai are taken with the 

 vegetable food. 





Movement of the Small Intestine 



The movements of the small intestine have been studied 1 the 



bismuth subnitrate and x-ray method, _ by observing them after 

 ing the abdomen of an animal subm< rged in a bath of physio'.. Jine 



at body temperature, (3) by observing the changes in pr< 

 in a thin-walled rubber balloon i i in the lumen 



connected with a recording tambour Pig. L60 . and 4 bj 



portions of the intestine and keeping them alive in a bath of Balin( 



tion at body temperature, through which oxygen is m. 



The Si o mi nti no Mo 1 



When a suitably fed animal is placed OH the hold, 

 by the x-ray method, no movement in the intestinal b! illy 



observed tor some time. The firsl movement to ap] 



one of the columns of food into small BegUN 



Each of these segments again quickly divid< 



halves suddenly unite to Eorm oev - in, in ■ nuu 



