Chap. XIV] THE DIGESTIVE SYSTEM 273 



wise through the gland, from the tail to the head. The pancreatic 

 and common bile duct enter by means of a common opening into 

 the duodenum about three inches (75 mm.) beyond the pylorus. 



Islands of Langerhans. — Scattered throughout the pancreas 

 are round or ovoid bodies known as the islands of Langerhans. 

 Each island is about one twenty-fifth inch (1 mm.) in diameter 

 and consists of a group of many-sided cells. They are surrounded 

 by a rich capillary network. Considerable evidence supports 

 the theory that the internal secretion of the pancreas is formed 

 by these islands. 



Function. — Two secretions are formed in the pancreas. (1) The 

 pancreatic juice, which is one of the most important of the diges- 

 tive juices, is an external secretion and is poured into the duodenum 

 during intestinal digestion. (2) The secretion formed by the 

 islands of Langerhans is an internal secretion that is absorbed by 

 the blood and carried to the tissues. This internal secretion aids 

 in the oxidation of glucose. 



Diabetes mellitus. — This is a disease characterized by a lack 

 of oxidation of glucose and its consequent loss to the body as it is 

 excreted in the urine. The cause is not settled, but it is believed 

 that disease of the pancreas involving the islands of Langerhans 

 may produce this condition. 



THE LIVER 



The liver (hepar) is the largest gland in the body, weighing 

 ordinarily from fifty to sixty ounces (1500 to 1800 grams). 

 It measures ten to twelve inches (25 to 30 cm.) from side to side, 

 six to seven inches (15 to 17.5 cm.) from front to back, and three 

 to four inches (7.5 to 10 cm.) from above downward in its thickest 

 part. It is a dark reddish brown organ, placed in the upper right 

 and middle portion of the abdomen,^ and extending somewhat into 

 the left hypochondriac region. The upper convex surface fits 

 closely into the under surface of the diaphragm. The under con- 

 cave surface of the organ fits over the right kidney, the upper por- 

 tion of the ascending colon, and the p.vloric end of the stomach. 

 The number five prevails in the parts and appendages of the liver. 



Ligaments. — The liver is held in place by five ligaments, four 

 of which are formed by folds of peritoneum, and the fifth, or round 



1 Right hypochondriac and epigastric regions. 



