THE PORTAL CIRCULATION 271 



stances, digestion is interfered with both in the stomach and 

 in the duodenum. 



In the absence of the pancreatic secretion, e.g., pancreatic 

 infantilism, and in obstruction to the outflow of the secretion 

 into the duodenum, the most striking feature is due to the 

 absence of the lipolytic enzyme. The digestion of fatty 

 substances is impossible and these constituents of the food 

 are passed unchanged in the faeces. The digestion of proteins 

 and carbohydrates is not so seriously disturbed, as they are 

 acted on by the saliva, the gastric juice and the succus 

 entericus. 



At birth, the amylolytic action of the pancreatic secretion 

 is not well developed, although its proteolytic and lipolytic 

 actions are quite normal. When it is remembered that the 

 saliva has little action on carbohydrates during the first year, 

 it becomes quite evident that starchy foods should not form 

 a part of the diet of the infant. 



In addition to the secretion which it pours into the intestine, 

 the pancreas possesses an internal secretion. This secretion 

 is formed by groups of polygonal cells, termed the " islands of 

 Langerhans," which have no connexion with the ducts of the 

 gland. It has been suggested that diabetes mellitus is due to 

 insufficiency of the pancreatic internal secretion and the 

 " islands " are found to be degenerated in a certain percentage 

 of cases. 



THE PORTAL CIRCULATION 



A special description of the portal vein and its tributaries 

 is rendered necessary owing to the frequency with which portal 

 obstruction occurs and owing to the important changes which 

 result from such obstruction. 



The Portal Vein is formed by the union of the superior 

 mesenteric and the splenic vein behind the neck of the pancreas. 

 From its origin it passes upwards, lying at first in front of the 

 head of the pancreas and later behind the first part of the 

 duodenum, where it comes into relationship with the bile 



