DIGESTIVE ORGANS SMALL INTESTINE. 



531 



Fig. 235. 



Fig. 236. 



are numerous follicles, 

 which, with the exhalants, 

 secrete a mucous fluid, 

 called by Haller succus 

 intestinalis. Their entire 

 number in the whole ali- 

 mentary canal is estimated 

 by Dr. Horner to be 46,- 

 900,000. 1 At about four 

 or five fingers' breadth 

 from the pylorus, the duo- 

 denum is perforated by 

 the termination of the 

 biliary and pancreatic 

 ducts, which pour bile 

 and* pancreatic fluids into 

 it. (Fig. 219.) Generally, 

 these ducts enter the in- 

 testine by one opening; 

 at times, they are distinct, 

 and lie alongside each ^' Longitudinal Section of the 



, o Jejunum, showing the 



Other. The Structure of Bloodvessels of Villi of the Villi as seen under the 



the duodenum is the same Hare> Microscope. 



flq that of thp whole of lj 1 ' Veins filled With Whlte *> * Terminal orifices of 



mi Section. 2, 2. Arteries filled the'villi. 2,2. Internal coats 



the intestinal Canal. The ^jJ^Ses between^he two 6 of the intestine. 3. Peritoneal 



muscular coat is, however, 



thicker, arid the peritoneal coat only covers its first portion, passes 

 before the second, and is totally wanting in the third, which we have 

 described as included in the transverse mesocolon. 



The other two portions of the small intestine are of considerable 

 length ; the jejunum commencing at the duodenum, 

 and the ileum terminating, in the right iliac fossa, in 

 the first of the great intestines the caecum. They 

 occupy the middle and almost the whole of the 

 abdomen, being surrounded by the great intestine 

 (Fig. 210). The jejunum is so called from being ge- 

 nerally found empty; and the ileum from its numerous 

 windings. The line of demarcation, however, be- 

 tween the duodenum and jejunum, as well as between 

 the latter and the ileum, is not fixed : it is an arbi- 

 trary division. The jejunum has, internally, the One of the Gianduiae 

 greatest number of valvulse conniventes and villi. S J La?g?Ztestfnef 

 The ileum is the lowest portion. It is of a paler as seen from above, 

 colour, and has fewer valvulse conniventes. The andalso 

 jejunum is situate at the upper part of the umbilical region ; the ileum 

 at the lower part, extending as far as the hypogastric and iliac regions. 

 The mucous membrane of the jejunum and ileum resembles, in all 

 essential respects, that of the duodenum; the valvulge conniventes are, 



Fig. 237. 



1 Special Anatomy and Histology, 7th edit., ii. 55, Philad., 1846. 



