5 TO JEJUNUM AND ILIUM. 



The mesentery (Fig. 184 B,) is a duplication of the perito- 

 neum, having its root at the spine, about six inches in 

 length, and extending obliquely from the second lumbar 

 vertebra on the left, to the right iliac fossa. On the cir- 

 cumference of this reflection are placed the intestines, 

 while between its laminae are found the blood-vessels, 

 nerves, lymphatic glands, and lacteals. 



The muscular coat is not so strong as in the duodenum, 

 though it is thought the two sets of fibres are more dis- 

 tinctly made out. They are pale and thin as in the duode- 

 num. The longitudinal set shortens the tube, while the 

 circular set constricts or lessens its diameter; the former pro- 

 ducing the peristaltic, the latter the vermicular motion of 

 the bowels. The conjoint action of the two carries on, step 

 by step, the contents of this tube. 



The mucous coat presents thevalvulee conniventes through, 

 the whole of the jejunum, more prominent than in the duo- 

 denum. These valves decrease as they descend, till in the 

 lower part of the ilium for about two or three feet they are 

 entirely absent. The mucous follicles are abundant and 

 exist every where, as in the duodenum and stomach, pre- 

 senting the usual cribriform appearance. The glands of 

 Peyer seem peculiar to the ilium, and are chiefly found at 

 its lower part and opposite the mesentery. They are seen 

 in clusters called glandulcc agminatce, (Fig. 25,) and present 

 patches of small, white, circular raised spots, varying in 

 size from a few lines to as many inches in length, and from 

 eight to twelve lines in breadth. 



These clusters are mostly elliptical in their shape, and 

 as many as thirty of them have been recognized in the 

 ilium, coming nearer and nearer to each other as they ap- 

 proach the termination of this intestine. The circular spots 

 composing these clusters have few if any villi over their 

 surface, but each one of them is observed to be surrounded 

 by a circle of minute openings leading to the follicles of 

 Lieberkuhn. There seems to be no connection between 

 these follicles and the glands of Peyer, as the latter have 

 no opening or excretory duct ; but on being ruptured are 



