MAMMALIA 277 



The intestine is resolved broadly into the small intestine 

 and the large intestine. The small intestine is divided up 

 into regions known as the duodenum and ileum. The duo- 

 denum is the first loop. It receives the bile duct near its 

 proximal end next the stomach and the pancreatic duct, an 

 exceptional position, near the middle of the far side of the 

 loop. 



The liver is a large red gland convex on its outer surface 

 next the diaphragm and fitting into the surface of the stomach 

 and the right kidney on the opposite aspect. It is resolved 

 into right and left lobes and into subdivisions of these. The 

 hepatic ducts combine to form the bile duct, and the right 

 hepatic duct expands on the inner side of the right lobe to 

 form the gall bladder, the duct of which is called the cystic 

 duct. The bile duct then passes to the duodenum. The 

 pancreas is in a simple state. The tubules of the gland lie in 

 the mesentery supporting the two limbs of the duodenum, 

 and the duct opens, as stated, on the distal part of the loop. 



The inner wall of the intestine generally is produced into 

 numerous papillae, called villi, and it also invades the sub- 

 mucosa to form many glands. On its walls islands of 

 lymphoid tissue occur, which are termed Peyer's patches. 



The upper part of the intestine receives, therefore, in asso- 

 ciation with the chyme passed from the stomach a supply of 

 bile which brings the food once more into an alkaline condi- 

 tion. Further along the duodenum it obtains the pancreatic 

 juice, and throughout its length it gains the products of the 

 intestinal glands, the secretion of which is called the succus 

 entericus. 



The bile has a lubricant action and it is antiseptic. It 

 aids but slightly in the digestion of fats and in converting 

 starch into a soluble state. The pancreatic secretion and the 

 secretion of the intestinal glands play a more active part in 

 digestion. In addition to the mucin, salts and water common 

 to all these secretions of the alimentary canal, these possess 

 important enzymes. Amylase acts upon starch, trypsin upon 

 nitrogenous substances, lipase upon fats. The result of the 

 action of the juices upon the food of the small intestine is to 

 reduce it largely to a soluble condition, from a colloid to a 



