152 



DIGESTION. 



Fie. 32. 



exert any digestive action on starch. The pancreatic juice, on the 

 other hand, has the property of converting starch into sugar ; but 

 it is not known whether this fluid be always present in the duode- 

 num. The true intestinal juice is the product of two sets of glan- 

 dular organs, seated in the substance of or beneath the mucous 

 membrane, viz., the follicles of Lieberkiihn and the glands of Brun- 

 ner. The first of these, or Lieberkiihii's follicles (Fig. 31), are the 

 most numerous. They are simple, nearly straight tubules, lined 

 with a continuation of the intestinal epithelium, and somewhat 

 similar in their appearance to the follicles of the pyloric portion of 

 the stomach. They occupy the whole thickness of the mucous 

 membrane, and are found in great numbers throughout the entire 

 length of the small and large intestine. 



The glands of Brunner (Fig. 32), or the duodenal glandube, as 

 they are sometimes called, are confined to the upper part of the duo- 

 denum, where they exist as a 

 closely set layer, in the deeper 

 portion of the mucous mem- 

 brane, extending downward a 

 short distance from the pylo- 

 rus. They are composed of 

 a great number of rounded 

 follicles, clustered round a 

 central excretory duct. Each 

 follicle consists of a delicate 

 membranous wall, lined with 

 glandular epithelium, and 

 covered on its surface with 

 small, distinctly marked nu- 

 clei. The follicles collected 

 around each duct are bound 

 together by a thin layer of 



areolar tissue, and covered with a plexus of capillary bloodvessels. 

 The intestinal juice, which is the secreted product of the above 

 glandular organs, has been less successfully studied than the other 

 digestive fluids, owing to the difficulty of obtaining it in a pure 

 state. The method usually adopted has been to make an opening 

 in the abdomen of the living animal, take out a loop of intestine, 

 empty it by gentle pressure, and then to shut off a portion of it 

 from the rest of the intestinal cavity by a couple of ligatures, 

 situated six or eight inches apart ; after which the loop is returned 



Portion of one of BKUN NEK'S 

 GLANDS, from Human Intestine. 



DUODENAL 



