292 



THE MAINTENANCE OF THE INDIVIDUAL 



passed to the ladeals. Beneath this is a mass of connective tissue 

 permeated by a network of capillaries that in turn surround the 

 central lymph channel (lacteal) into which fat is absorbed. Between 

 the villi are found the openings of the intestinal glands which 

 are associated with the compound duodenal glands in the production 

 of intestinal juice. Aggregations of two types of lymph nodules 

 appear, solitary lymph nodes about the size of a pin head and groups 

 spoken of as Peyer^s patches. The latter are sometimes the seat of 

 local inflammation and ulceration as in typhoid fever. 



The same four coats which were found about the stomach occur 

 in the small intestine except that the oblique layer of muscles is 

 missing, while the mucous layer is very thick and vascular. 



The Large Intestine. The large intestine of man has somewhat 

 the same anatomical structure as the small intestine except that it 

 lacks villi and has a greater diameter. It is separable into a shallow 

 blind pouch at the juncture of the small and large intestines, and an 

 enlarged colon and rectum, terminating with the anus. The entrance 

 of material into the large intestine is regulated by the ileo-caecal 

 valve, formed by two flaps of mucous membrane, which permits entry 

 into it but effectively prevents back flow. At the end of the caecum 



is a A'estigial continuation of 

 it, the vermiform appendix, a 

 blind pouch usually about three 

 inches long. Inflammation of 

 this structure usually results 

 in a condition recognized as 

 appendicitis. 



The colon of man is divisible 

 into four parts known respec- 

 tively as the ascending, trans- 

 igrr?oJd verse, descending, and sigmoid 

 -Oiorv colons. In other mammals, 

 the colon may not always be 

 rectum separated into these parts 



The caecum, appendix, and colons of although the juncture of the 

 man. Why is the appendix so frequently .n^alland large intestines is 

 the seat ol bacterial inlections.J ^ 



clearly set off by an ileo-caecal 



valve and a caecum. The anus is guarded by both an external and 

 an internal sphincter which keep the orifice closed except during 

 defecation. The external sphincter is composed of striated muscle 



caecum 



appendi 



