WORK DONE BY THE PANCREAS 



155 



Proteins, under the same conditions, are broken down into amino- 

 acids. Fats, which so far have been unchanged except to be 

 melted by the heat of the body, are changed by the action of 

 the pancreatic fluid and the bile into substances which can pass 

 through the walls of the food tube. If we test pancreatic fluid, 

 we find it strongly alkaline in its reaction. If two test tubes, one 

 containing olive oil and water, the other olive oil and a weak 

 solution of caustic soda (which has an alkaline reaction) arc 

 shaken violently and then 

 allowed to stand, the oil and 

 water will quickly separate, 

 while the oil and solution of 

 caustic soda will remain for 

 some time in a milky emul- 

 sion. If this emulsion is ex- 

 amined under the microscope, 

 it will be found to be made of 

 millions of little droplets of 

 fat, floating in the liquid. 

 The presence of the caustic 

 soda helped the forming of the 

 emulsion. Pancreatic fluid 

 emulsifies fats and changes 

 them into fatty acids and 

 soft soaps. Fat in these forms 

 can be absorbed. The above 

 changes are brought about by 

 three enzymes, amylase, which 



breaks down starches to simpler sugars ; try p^ sin, which, working 

 with other enzymes of the small intestine, breaks protein into 

 amino-acids ; and lip'ase, which breaks the fats into fatty acids 

 and glycerin. These fatty acids become soap when mixed with the 

 alkaline material in the intestinal juice. 



Conditions in which the Pancreas does its Work. — The secre- 

 tion of the pancreatic juice is brought about by the action of a 

 hormone called secre'tin} This substance, which is formed in some 

 of the cells lining the small intestine just below the pylorus, is 



1 See page 148- 



Appearance of milk under the micro- 

 scope, showing the natural grouping of the 

 fat globules. In the circle a single group 

 is highly magnified. Milk is one form of 

 an emulsion. (S. M. Babcock, Wis. Bui. 

 No. 61.) 



