CH. xxxii.] PANCREATIC JUICE. 4 8 9 



3. Action on Fats. The action of pancreatic juice on fata 

 is a double one : it forms an emulsion, and it decomposes the fats 

 into fatty acids and glycerin by means of its fat-splitting ferment 

 steapsin. The fatty acids unite with the alkaline bases to form 

 soaps (saponificatiori). The chemistry of this is described on 

 p. 392. The fat-splitting power of pancreatic juice cannot be 

 studied with a glycerin extract, as steapsin is not soluble in 

 glycerin : either the fresh juice or a watery extract of pancreas 

 must be used. 



The formation of an emulsion may be studied in this way. 

 Shake up olive oil and water together, and allow the mixture to 

 stand ; the finely divided oil globules soon separate from and 

 float on the surface of the water ; but if a colloid matter like 

 albumin or gum is first mixed with the water, the oil separates 

 more slowly. A more permanent emulsion is formed by an 

 alkaline fluid, and especially when a small amount of free fatty 

 acid is being continually liberated ; the acid combines with the 

 alkali to form a soap. Pancreatic fluid possesses all the necessary 

 qualifications for forming an emulsion : 

 i. It is alkaline. 



ii. It is viscous from the presence of proteid. 

 iii. It has the power of liberating free acids. 



4. Milk-curdling Ferment. The addition of pancreatic 

 extracts or pancreatic juice to milk causes clotting; but this 

 action (which differs in some particulars from the clotting caused 

 by rennet) can hardly ever be called into play, as the milk upon 

 which the juice has to act has been already curdled by the rennin 

 of the stomach. 



Intestinal Digestion. 



The pancreatic juice does not act alone on the food in the 

 intestines. There are, in addition, the bile, the succus entericus 

 (secreted by the crypts of Lieberkiihn), and bacterial action to be 

 considered. 



The bile, as we shall find, has little or no digestive action by 

 itself, but combined with pancreatic juice it assists the latter in 

 all its actions. This is true for the digestion of starch and of proteid, 

 but most markedly so for the digestion of fat. Occlusion of the 

 bile-duct by a gall-stone or by inflammation prevents bile entering 

 the duodenum. Under these circumstances the fccces contain a 

 large amount of undigested fat. 



The succus entericus appears to have to some extent the- 

 power of converting starch into sugar ; whether it acts on proteids 



