DIGESTION. 53 



(1) Solitary glands consist of a rounded mass of whitish adenoid 

 tissue about ^ to y 1 ^- in. in diameter, situated in the submucous 

 tissue, but often projecting to the surface of the intestine. Each 

 lymphoid mass is surrounded by Lieberkiihn's follicles. 



(2) Agminate glands (Peyer's patches) consist of groups of these 

 adenoid masses, making " patches " in the mucous membrane i to 3 

 in. long and about in. wide. 



What is the function of the intestinal glands ? 



Secretion of the intestinal juice (succus entericus). 



What is the function of the intestinal juice ? 



Its effect upon digestion is not fully understood, but it probably 

 has some effect upon saccharose, and possibly upon proteids, con- 

 verting the one into glucose and the other into peptones. However, 

 its chief function seems to be to supply the loss of fluid to take 

 the place of that which is absorbed as digestion progresses. At 

 any rate, the contents of the small intestine as they enter the colon 

 are about as fluid as when they leave the stomach. 



What other glands discharge their secretions into the small in- 

 testine ? 

 The pancreas and the liver. 



Describe the pancreas. 



The pancreas is an organ lying in the upper part of the abdo- 

 men in contact with the duodenum : in length it is about 6 in., and 

 is thicker at its right or duodenal end. It is a conglomerate gland, 

 resembling in structure the salivary glands. During digestion it is 

 active, but is quiescent in the intervals. Its secretion, pancreatic 

 fluid, is discharged into a main duct which receives branches from 

 the lobes of the gland, and is emptied with the bile through a com- 

 mon opening about 2 or 3 in. beyond the pylorus. During digestion 

 the cells of the organ become granular, and the granules are thought 

 to consist of the substance from which the ferments of the pancreas 

 are derived, zymogen, rather than of the ferments themselves. 



What are the characteristics of pancreatic secretion ? 



The pancreatic juice is a clear, colorless fluid, having an alkaline 

 reaction and a notably viscid consistency. It coagulates with heat, 

 and is made quite gelatinous by cold. Specific gravity, 1015. Its 

 composition varies, but in general is as follows : 



