THE LARGE INTESTINE. 371 



large intestine. The character of the intestine gradually changes from 

 its upper to its lower end, so that portions of the two intestines'^ remote 

 from each other, present certain well-marked differences of structure, 

 which may be here enumerated. Thus, the jejunum is wider, and its 

 ';oats arc thicker ; it is more vascular, and therefore it has a deeper 

 colour ; its valvnlfe conniventes are long, wide and numerous ; its villi 

 are well developed ; and the patches of Peyer's glands are smaller, less 

 frequent, and sometimes confined to its lower part. The ileum, on the 

 other hand, is narrower; its coats are thinner and paler ; the valvulte 

 conniventes are small, and gradually disappear towards its lower end ; 

 the vilh are shorter ; and the groups of Fever's glands are larger and 

 more numerous. The diameter of the jejunum is al)out one inch and a 

 half, that of the ileum about one inch and a quarter. A o-iven length 

 of the jejunum weighs more than the same of the ileum. 



At a point in the lower part of the ileiun it is not very tincommou to find a 

 pouch or durrficidi/m given off from the main tube. The origin of these 

 diverticula is explained by reference to the history of development, from which 

 it appears that they arise from a portion of the ductus vitello-intestinalis. or 

 tube imiting the intestine with the umbilical vesicle, remaining pervious. They 

 are not to be confounded with hernial protrusions of the mucous membrane, 

 which may occur- at any pomt. 



THE LARGE INTESTINE. 



The large intestine extends from the termination of the ileum to the 

 anus. It is divided into the crecum (including the vermiform appendix), 

 the colon and the rectum ; and the colon is again subdivided, according 

 to Its direction, into four parts, called the 'ascendino-, transverse, and 

 desccndmg colon, and the sigmoid flexure. 



The length of the large intestine is usually about five or six feet ; 

 being about one-fifth of the whole length of the intestinal canal. Its 

 diameter, which greatly exceeds that of the small intestine, varies at 

 different points from two inches and a half to about one inch and a 

 half. It diminishes gradually from its commencement at the CKCum to 

 its termination at the anus ; excepting that there is a well-marked 

 dilatation of the rectum just above its lower end. 



In outward form, the greater part of the large intestine differs 

 remarkably from the small intestine ; for, instead of constituting an 

 even cylindrical tube, its surface is thrown into numerous sacculi, 

 marked off" from each other by intervening constrictions, and arranged 

 in three longitudinal rows, separated by three strong flat bands of 

 longitudinal muscular fibres. This sacculated structure is not found in 

 the rectum. 



Sa?RUCTURE OF THE LARGE INTESTINE. 



The large intestine has four coats, like those of the stomach and 

 smaU intestine, namely, the serous, muscular, areolar or submucous, and 

 mucous. 



The serous coat is quite similar to that of the small intestine, except 

 that, along the colon and upper part of the rectum, it is developed into 

 numerous little projections, which enclose a certain amount of fat, and 

 are termed cqypendkes cpqMccc. 



The muscular coat, like that of the other parts of the intestinal 



