60 Animal Husbandry 
21 times as great. There seems to be experimental evidence 
showing that vegetable fat becomes deposited in the animal 
without change, whereas fat formed from carbohydrates in- 
volves complex transformation. 
DIGESTIBILITY OF FOOD 
The value of food depends on the digestibility of the various 
materials of which it is composed, and not alone on its composition 
as shown by a chemist. In order to get a clear conception of 
digestion, it will be necessary to review briefly the process through 
which the food materials must pass on their way from the food to 
the flesh or energy of the animal body. 
114. Digestion. — The process of digestion is largely a process 
of solution, aided to a certain extent by chemical changes that take 
place through the influence of various ferments with which the 
food comes in contact as it passes through the digestive tract. 
The digestive organs form a canal through the body, and the food 
in its passage through this tract or canal is acted upon by various 
fluids. Each fluid has a special work to do in the process of 
digestion. The food is taken into the mouth, where it is reduced 
to fine particles in order that the digestive juices may better do 
their work and in order to put it into condition to be swallowed. 
During this mastication, a digestive fluid, called saliva, is poured 
upon the food, moistening it and changing a part of the starch to 
sugar. After leaving the mouth the food passes down the esoph- 
agus into the stomach, where the digestive fluid, called gastric 
juice, is poured upon it, changing part of the protein. When the 
food leaves the stomach, it enters the small intestines, where it 
comes in contact with two digestive fluids — the bile from the 
liver, and the pancreatic juice from the pancreas. The bile 
prepares the partly digested food for the action of the pancreatic 
juice and changes the fats. The pancreatic juice has a more 
complex function. It contains at least three distinct ferments, 
