THE STORY OF DIGESTION 51 



the tip of the tongue lying to the right side of the 

 body. The duct or tube of the sweetbread leads 

 into the intestine, and may join the duct of the liver 

 itself. The sweetbread is an organ devoted to the 

 secretion of the sweetbread or pancreatic juice, 

 manufactured from the blood supplied to the cells of 

 the organ. It is a clear fluid of complicated com- 

 position. At least four different ferments are 

 contained in it. These are represented first by a 

 substance known as trypsin which acts on the nitro- 

 genous foods so that any of these foods which have 

 escaped the action of the gastric juice of the 

 stomach will be altered and changed into peptones in 

 the intestine. A second ferment is that known as 

 amylopsin, this substance acting as does the ptyalin 

 of the saliva and changing starch into sugar. Here, 

 again, we meet with an expedient of nature whereby 

 starchy foods which may have passed unchanged 

 into the intestine will be acted upon and duly con- 

 verted into sugar by the sweetbread secretion. A 

 third ferment, called steapsin, acts on fats, and 

 therefore must assist the work of the bile, whilst a 

 fourth ferment is known as rennin, this last curdling 

 milk. The sweetbread secretion derives its impor- 

 tance from the fact that it is the only digestive fluid 

 which can act upon all kinds of food, nitrogenous 

 and non-nitrogenous alike. Recent researches seem 

 to show that the sweetbread also manufactures what 

 is called an internal secretion not meant to be 

 poured upon the food, but to be passed into the 

 blood. It is supposed that this latter ferment tends 

 to destroy or otherwise to change or utilise sugar 

 which has passed into the blood. Hence in cases of 

 diabetes, already mentioned, it is supposed that 

 where this internal secretion of the sweetbread fails 



