IOO THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



tericus. The former are chiefly limited to the upper half of 

 the duodenum. The latter exist throughout the small and 

 large intestine. 



4. The solitary and agminate glands are not supposed to 

 contribute to the production of the intestinal juice. They are 

 alike in structure, the agminate glands being only a collection 

 of solitary glands. The former are the Peyer's patches, so 

 important in the pathology of typhoid fever. These patches 

 are usually about twenty in number and confined to the lower 

 two-thirds of the ileum, where they occupy that portion of 

 the circumference of the tube opposite the attachment of the 

 mesentery. Their average dimensions are I X i l /2 in. They 

 consist essentially of lymphoid tissue, the separate follicles of 

 which are surrounded by lymphatics and penetrated by 

 blood-vessels. They are covered by villi, but the valvulae 

 conniventes cease at their edges. The solitary glands are 

 more widely distributed than the agminate. 



The chyme, having passed from the stomach to the small 

 intestine, encounters three digestive fluids, pancreatic juice, 

 bile and intestinal juice. These are, of course, mixed to- 

 gether, but none interferes with the action of the other. 



The Pancreas. The pancreas is a large gland lying in the 

 upper part of the abdominal cavity behind the stomach. It 

 has the general shape of a hammer, its head being embraced 

 by the bend of the duodenum and its opposite extremity 

 reaching to the spleen. It weighs some four or five ounces, 

 and is about seven inches long. Its duct, the duct of Wir- 

 sung, usually joins the common bile duct just where this lat- 

 ter penetrates the wall of the duodenum, so that the bile and 

 pancreatic juice enter the small intestine together. Some- 

 times the two ducts do not join, and sometimes a second 

 smaller duct from the pancreas penetrates the duodenum a 

 little below the larger one. The duct of Wirsung traced 

 backward divides and subdivides until its final ramifications 

 end in the alveoli, or secreting portions. 



Histology. This is a compound tubular gland. The cells 



