100 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



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 mes- 

 entery. Their average dimensions are iXiJ 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 in- 

 testine, encounters three digestive fluids, pancreatic juice, bile 

 and intestinal juice. These are, of course, mixed together, 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 Wirsung, usually 

 joins the common bile duct just where this latter penetrates the 

 wall of the duodenum, so that the bile and pancreatic juice 

 enter the small intestine together. Sometimes the two ducts do 

 not join, and sometimes a second smaller duct from the pan- 

 creas 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. 



