ORGANS OF DIGESTION. 



Fig. 337. Patch of Peyer's Glands. 

 From the lower part of the Ileum. 



^ Peyer's glands may be regarded as aggregations of solitary glands, forming 

 circular or oval patches from twenty to thirty in number, and varying in length 

 from half an inch to four inches. They are largest and most numerous in the 

 ileurn. In the lower part of the jejunum they are small, of a circular form, and few 

 in number ; they are occasionally seen in the duodenum. They are placed lengthwise 

 in the intestine, covering the portion of the tube most distant from the attachment 



of the mesentery. Each patch is formed 

 of a group of small, round, whitish vesicles, 

 covered with mucous membrane. Each 

 vesicle consists of a moderately thick ex- 

 ternal capsule, having no excretory duct, 

 and containing an opaque white secretion. 

 Each is surrounded by a zone or wreath of 

 simple follicles, and the interspaces between 

 them are covered with villi. These vesicles 

 are usually closed ; but it has been supposed 

 that they open at intervals to discharge the 

 secretion contained within them. The mu- 

 cous and submucous coats of the intestine 

 are intimately adherent, and highly vascular, 

 opposite the Peyerian glands. Their use is 

 not known [but they are now generally sup- 

 posed to belong to the lymphatic system]. 

 They are largest and most developed during 

 the digestive process. 



THE LARGE INTESTINE. 



Fig. 338. A portion of the above magnified. The Large Intestine extends from the 



termination of the ileum to the anus. It 

 is about five feet in length ; being one-fifth 

 of the whole extent of the intestinal canal. 

 It is largest at its commencement at the 

 ceecum, and gradually diminishes as faf as 

 the rectum, where there is a dilatation of 

 considerable size, just above the anus. It 

 differs from the small intestine in its greater 

 size, its more fixed position, and its saccu- 

 lated form. The large intestine, in its 

 course, describes an arch, which surrounds 

 the convolutions of the small intestine. It 

 commences in the right iliac fossa, in a 

 dilatation of considerable size, the ca3cum. 

 It ascends through the right lumbar and 

 hypochondriac regions, to the under surface 

 of the liver ; passes transversely across the 

 abdomen, on the confines of the epigastric 



and umbilical regions, to the left hypochondriac region ; descends through the 

 left lumbar region to the left iliac fossa, where it becomes convoluted, and forms 

 the sigmoid flexure ; finally, it enters the pelvis, and descends along its posterior 

 wall to the anus. The large intestine is divided into the ca3cum, colon, and rectum. 

 The Caecum (csecus, blind) is the large blind pouch or cul-de-sac extending 

 downwards from the commencement of the large intestine. It is the most dilated 

 part of this tube, measuring about two and a half inches, both in its vertical and 

 transverse diameters. It is situated in the right iliac fossa, immediately behind 

 the anterior abdominal wall, being retained in its place by the peritoneum, which 

 passes over its anterior surface and sides ; its posterior surface being connected by 





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