GR.\SSES OF IOWA. 467 



The gastric juice contains hydrochloric acid, as maybe seen 

 from the above analysis. This acid renders the ptyalin of the 

 saliva inactive as soon as the food is acted upon by the gastric 

 juice. In addition to the acid there is also present a ferment 

 called pepsin. It has been seen that the ptyalin changes 

 starch to sugar, but pepsin changes the albuminoids into a 

 peculiar class of substances called peptones. 



Albuminoids and peptones differ very little in their chemical 

 composition, and the following analyses will give a fair repre- 

 sentation of these bodies. 



PER CENT 



CarboD v. 51.5 54.5 



Hydrogen 6.9 7.3 



Oxygen 20.9 23.5 



Sulphur 3 2 



Nitrogen 15 2 17.0 



The action of the gastric juice is largely that of changing 

 the intoluble albuminoids to the soluble substances, or in 

 other words, peptones, and from the analysis we find that 

 there is little or no change in the chemical composition. 



After the action of the gastric juice in the stomach, the food 

 mateiial passes to the intestines, here a secretion of the pan- 

 creas, called the pancreatic juice, acts upon it. The pancreatic 

 juice is alkaline, and the action of the gastric juice ceases its 

 action, as its action is only carried on in the presence of acids. 



The pancreatic juice on analysis is found to be composed as 



follows: 



Dog. Horse. 



Water 980.45 982 50 



Solids 19.55 17.50 



Organic solids 12.71 8.88 



Ash 6.84 8.62 



Sodium 3.31 



Chlorides 3.43 



Phosphates .09 



Magnesium .01 



In the organic solids present in the pancreatic juice there 

 are present three ferments, each of which take an active part 

 in changing the food which has not been acted upon by the 

 ptyalin and pepsin. These ferments are as follows: 



I. Trypsin, changes proteids or albuminoids to peptones 

 and amido acids. 



II. Amylopsin changes starch to sugar. 

 30 



