INTESTINAL DIGESTION. 2^7 



being four times the length of the body in the cat, whereas 

 it attains extraordinary dimensions in herbivorous quadru- 

 peds, measuring 27 times the length of the body in the sheet) 

 and goat, 20 times in the ox, 12 in the horse, 11 in the ass 

 and mule, 15 in the dromedary, and again only 6 in the do^ 

 as a flesh-feeding animal. 



Not only the attachments, but also the shape of the intes- 

 tine, vary at different parts of its course, so that it has been 

 deemed necessary to divide it, either arbitrarily or at natural 

 demarcations. Thus we speak of the small and large intes- 

 tine, the two being separated naturally by a marked change 

 in direction, size, and conformation. 



Small Intestine. This, the smallest although longest, is 

 also the first portion of the intestinal tube, extending from 

 the pylorus to its sudden termination into the large intes- 

 tine. In it the food is subjected to the modifying influence 

 of important secretions, whereby its nutritive parts are fitted 

 for absorption by the vessels which for this purpose are 

 arranged in this portion of the intestinal track. 



The small intestine has been divided into three parts : this 

 classification is, however, purely conventional. Since it does 

 not recognise anatomical differences for its basis, it might 

 justly be presumed that this distinction of human anatomists 

 exhibited traces of imperfection, even when applied to the 

 frame of man. Such being the case, it is no matter of sur- 

 prise that, in referring the distinction to the intestinal canal 

 of animals, the incongruities of the system should le still 

 more apparent. 



Extending from the pylorus, the first portion is termed 

 the duodenum, from its being considered as twelve fingers*' 

 breadth in length : it is, however, extended round to the left 

 side of the spine, posteriorly to the anterior mesenteric artery. 

 The middle or floating portion of gut takes the name of 



