THE LIVER. 239 



Formerly it was considered that the secretion of pancreatic juice 

 is a reflex act brought about by stimulation of the afferent fibers 

 of the mucous membrane of the stomach or intestine, or both, by 

 the gastric juice, but, according to Bayliss and Sterling, it is due 

 to the production by the duodenal glands, as a result of the action 

 of the gastric juice, of a substance termed by them secretin, which 

 is taken up by the blood and, being carried to the pancreas, stimu- 

 lates that gland to the secretion of the pancreatic juice. 



Fleig claims that the soaps formed in the small intestine as a 

 result of the saponification of the fats of the food, produce by their 

 action on the mucous membrane sapokrinin, which is absorbed and 

 carried to the pancreas by the blood, where it stimulates that gland, 

 thus aiding in the secretion of pancreatic juice. 



Internal Secretion of the Pancreas. This organ has 

 been removed from animals without producing an immediately 

 fatal result, but in every such case sugar has appeared in the 

 urine, producing a condition denominated glycosuria, and this, too, 

 when no carbohydrate was present in the food. The urine has 

 also been increased in quantity, thirst and hunger have been 

 marked, and emaciation and muscular weakness have set in, with 

 death resulting in one or two weeks. If the gland is not entirely 

 removed, so little as one-fourth or one-fifth being left, glycosuria 

 does not occur, and, what is still more remarkable is, that after 

 the removal of the gland, if a portion of it is grafted under the 

 skin, or if the ducts are closed so as to prevent the secretion from 

 entering the duodenum, glycosuria is also absent. All of which 

 goes to prove that besides the pancreatic juice, which may be re- 

 garded as the external secretion of the pancreas, it also produces 

 an internal secretion which, taken up by the blood or lymph, either 

 aids in destroying the sugar produced by the liver or muscles, or 

 else inhibits the glycogenic function of these organs. The cells 

 which are believed to form this secretion have been described in 

 connection with the pancreas (p. 231). 



THE LIVER. 



This organ is situated in the abdominal cavity, and is as large 

 as all the other glands of the body taken together. Its transverse 

 diameter is 28 cm., anteroposterior diameter, 20 cm., and vertical 

 diameter, 6 cm. (Fig. 134). Its blood-supply is from the portal 

 vein and hepatic artery, while its nervous supply is from the left 

 vagus and celiac plexus. It is covered by the peritoneum, and 

 beneath this is the fibrous coat, which, at the transverse fissure, is 

 continuous with Glisson's capsule. This connective-tissue envelope 

 covers the hepatic artery, portal vein, and hepatic duct, and accom- 

 panies them through passages in the liver, the portal canals. 



Chemical Composition. The liver during life is alkaline, 



