M4 PHYSIOLOGY FOR BEGINNERS CHAP. 



of the duodenum, supported by a portion of the mesentery. 

 It is a large racemose gland like a salivary gland in struc- 

 ture. Its duct passes obliquely through the wall of the 

 duodenum and opens into the interior. By passing through 

 the intestine wall obliquely, a kind of valve is formed, so that 

 the pancreatic juice can pass readily into the intestine, but the 

 contents of the latter cannot pass into the duct. 



Composition and Action of Pancreatic Juice. 

 The pancreatic juice is a colourless, rather viscid fluid, con- 

 taining, besides a small quantity of proteids, certain salts, the 

 chief being sodium carbonate, which gives it an alkaline re- 

 action. It also contains certain ferments, by means of which 

 it acts on three classes of food-stuffs. It changes starch to 

 sugar,- like saliva ; proteids to peptone, like gastric juice ; and 

 it also acts on fats. These three actions are due to three 

 separate ferments. The ferment acting on starch, turning 

 starch into sugar, is called the amylolytic ferment, the one 

 acting on proteids, turning proteids into peptone, is called the 

 proteolytic ferment, and is also called trypsin. The ferment 

 acting on fats is the fat-decomposing ferment, and has the 

 power of decomposing fat into the fatty acid and glycerine 

 of which a fat is chemically composed. 



Obtain the pancreas of a recently-killed pig, chop it up very 

 fine, and put it to soak with a little sodium carbonate solution 

 (i per cent) in the warm ; after some hours strain off the fluid. 

 This fluid will be very like normal pancreatic juice, and will 

 convert starch into sugar and proteids into peptone. Prove 

 this in the same way that you did in the case of saliva and 

 gastric juice respectively. 



Composition of Bile. Bile is formed by the liver 

 and is conducted from it by a canal called the bile duct. 

 Before the bile duct leaves the liver it gives off a short side 

 branch which leads to the gall - bladder, situated at the 

 front of the under surface of the liver, and then leaving the 

 liver, passes to the duodenum, where it unites with the end of 

 the pancreatic duct, so that the two form a single tube through 

 the wall of the duodenum, and open together into the cavity 

 of the intestine. When digestion is not going on, the bile 

 formed passes along the side branch of the bile duct to the 

 gall-bladder, where it is stored. 



