736 



ORGANS OP DIGESTION. 



line in diameter, consisting of a closed saccular cavity, having no excretory 

 duct, and containing an opaque white secretion. Their free surface is covered 

 with villi, and each gland is surrounded by openings like those of the follicles 

 of Lieberkiihn. Their use is -ot known. 



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 

 ileum. 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 external 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 is supposed they open at intervals to 

 discharge the secretion contained within them. The mucous and submucous 

 coats of the intestine are intimately adherent, and highly vascular, opposite the 

 Peyerian glands. Their use is not known. They are largest and most devel- 

 oped during the digestive process. 



THE LARGE INTESTINE. 



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 intes- 

 tinal canal. It is largest at its commencement at the cascum, and gradually 



Fig. 403. Patch of Peyer's Glands. 

 From the lower part of the Ileum. 



Fig. 404. A portion of the above maguifled. 



m. 



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diminishes as far 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 sacculated 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 dilated part, the crocum. 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 epi- 

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

 through the left lumbar region to the left iliac fossa, where it becomes convo- 

 luted, and forms the siunnoid flexure; finally, it enters the pelvis, and descends 

 along its posterior wall to the amis. The large intestine is divided into the 

 caecum, colon, and rectum. 



