THE ANIMAL BODY DIGESTION METABOLISM 19 



which is doing no work and yielding no material product, so that it will 

 neither gain nor lose in weight. 



35. The alimentary canal. The alimentary canal should be considered 

 as a long, winding tube passing thru the animal from mouth to vent, 

 enlarged in places for the storage of food or waste. It includes the 

 mouth, gullet, stomach, small intestine, and large intestine. Within its 

 linings are organs which secrete the various fluids of digestion, and 

 into it, from other organs located near by, pour still other digestive 

 fluids. Within its walls are nerves controlling its action, arteries which 

 nourish it with fresh blood, and veins and lymphatics which absorb 

 and carry from it the products of digestion. It should be borne in mind 

 that the contents of the stomach and intestines are really outside the 

 body proper. Only when a substance has passed into or thru the walls 

 of the digestive tract has it actually entered the body of the animal. 



Ruminants (animals which chew the cud), including the ox, sheep, 

 and goat, have much more complicated digestive tracts than other 

 animals. In the horse and pig the gullet, or esophagus, is a simple 

 muscular tube passing from the mouth to the stomach. On the other 

 hand, in ruminants the gullet is expanded just before the true stomach, 

 or abomasum, is reached into three compartments of great aggregate 

 capacity, the first of which is the paunch, or rumen; the second, the 

 honeycomb, or reticulum ; and the third, the manyplies, or omasum. Of 

 the four stomachs the paunch is by far the largest, providing over 80 per 

 ct. of the total capacity of all the stomachs in the full-grown ox. The 

 inside lining of each compartment differs in appearance. The lining of 

 the paunch is somewhat like coarse velvet, due to myriads of small pro- 

 jections; the honeycomb is so called on account of its honeycomb-like 

 lining; and the manyplies is so named because its lining forms many 

 folds or leaves. 



The four stomachs of the full-grown ox have a combined capacity of 

 120 to 180 quarts or more. In young ruminants the first three stomachs 

 are much less developed than in mature animals. For example, in a 

 young calf, the abomasum will have a considerably larger capacity than 

 the paunch, the honeycomb, and the manyplies, combined. 



In the horse and the hog, the stomach is simple, consisting of but a 

 single sac, much like the stomach of man. The stomach of the horse has 

 a capacity of only 12 to 19 quarts, being small indeed compared with the 

 capacity of the stomachs of the ox. The stomach of the pig holds about 

 8.5 quarts. The fourth stomach, or abomasum, of ruminants corresponds 

 to the single stomach of these other animals. 



The small intestine is the long, folded, winding tube into which the 

 stomach empties. In the mature ox it is about 2 inches in diameter and 

 130 feet long, or about 20 times the body length. In horses it is 70 

 to 75 feet long, in sheep 80 feet, and in swine 60 feet. Its average 

 capacity is about as follows: Cattle, 70 quarts; horses, 50 to 65 quarts; 

 sheep and swine, 10 quarts. 



