New York AGRICULTURAL EXPERIMENT STATION. 157 
quantity of free acid present. Lactic and butyric and other 
acids when present are secondary products, arising either by 
their respective fermentations from articles of food, or from the 
decomposition of their alkaline or other salts. In man the 
amount of free hydrochloric acid in healthy juice may be stated 
to be about .2 per cent, but in some animals it is probably 
higher. 
On starch and dextrose gastric juice has no action. An exces- 
Sive quantity of cane sugar introduced into the stomach causes a 
secretion of mucus, and hence provides for its own conversion 
into dextrose. On Jats gastric juice has at most a limited action. 
- When adipose tissue is eaten, the chief change which takes place 
a in the stomach is that the proteid and gelatiniferous envelopes of 
the fat-cells are dissolved, and the fat set free. Though there is 
| experimenta! evidence that emulsion of fats to a certain extent 
q does take place in the stomach, the great mass of the fat of a 
| ~meal is not so changed. 
On proteids the action of the gastric juice is to convert the 
insoluble into soluble proteids. When the conversion is com- 
plete peptones are formed, the most soluble of all proteids; if the 
conversion is not complete, the proteids are left in one of the 
intermediate stages, namely, in the form of albwmose or 
parapeptone. 
The active principle of the gastric juice is a ferment body to 
which the name pepsin has been given. 
Bile, action on food. In some animals at least bile contains a 
ferment capable of converting starch into sugar; but its action in 
this respect is wholly subordinate. 
On proteids bile has no digestive action whatever, but being, 
generally at least, alkaline, and often strongly so, tends to neutral- 
ize the acid contents of the stomach as they pass into the duodenum 
and so prepares the way for the action of the pancreatic juice. 
With regard to the action on fats, the following: statements 
may be made: : 
Bile has a slight solvent action on fats, as seen in its use by 
painters. It has by itself a slight but only slight emulsifying 
power; a mixture of oil and bile separate after shaking rather 
less rapidly than a mixture of oil and water. With fatty acids 


