394 INTERNAL PARASITES. 



hard palate forms the roof of the mouth, and the soft palate is the mem- 

 branous curtain which divides the mouth from the pharynx. The 

 incisor (front) teeth are used for seizing and cutting the food, when, as in the 

 case of growing grass, it offers resistance to its introduction into the mouth. 

 The molar (back) teeth are grinders. As the lower jaw is much narrower 

 than the upper jaw, the horse can chew his food only on one side of his mouth 

 at a time. 



The PHAEYNX (p. 350) is a cavity common to the alimentary canal and 

 the air passages. 



.THE GULLET (oesophagus) is the tube which carries food from the pharynx 

 to the stomach. In the first half of its course down the neck, it lies above the 

 windpipe, and then becomes inclined to the left of it. 



The STOMACH of the horse is comparatively small, as it can hold on an 

 average, only from 3 to 3^ gallons. 



THE SMALL INTESTINE is the continuation of the alimentary canal from 

 the stomach. It is about 72 feet long, 1^ inches in diameter, is doubled many 

 times on itself, and it leads into a large sac, called the ccecum, which is the 

 animal's chief water reservoir, and which is capable of containing on an 

 average about 7^ gallons of fl'uid. 



THE LARGE INTESTINE is made up of the ca?cum, Inrge colon, and 

 the smill colon. The laraje or double colon is a wide canal which begins 

 at the caecum and ends at the commencement of the small colon. It consists 

 of a succession of dilatations and contractions, and occupies the position of a 

 loop doubled on itself. It is generally about 12 feet through its entire length. 

 It is capable of containing about 18 gallons, and it communicates with the 

 small or -floating colon, which is about 10 feet long, and is folded several times 

 on itself, in a manner somewhat similar to that of the small intestine. 'J he 

 posterior end of the small colon (the rectum) takes a straight course from 

 the front of the pelvis to the anus. 



STRUCTURE OF THE STOMACH AND INTESTINES.— These organs 

 are composed of a mucous membrane, which lines their interior ; a muscular 

 coat, which covers this mucous layer ; and a serous coat, Avhich is the smooth 

 ajid glistening membrane we see on the outside of the stomach and intestines 

 of the dead body of an animal whose abdomen has been opened. 



GLANDS WHICH DISCHARGE FLUIDS INTO THE ALIMENTARY 

 CANAL. — The salivary glands are situated in various positions near the 

 mouth, into which they pour their respective secretions (saliva). The largest 

 of them is the parotid gland, which is behind the lower jaw, and close to the 

 ear. The most important salivary glands exist in pairs, one on each side of 

 the head. The right side of the stomach is largely supplied with small glands 

 which pour gastric juice into that organ. The surface of the left side of the 

 stomach is similar to that of the gullet. A duct carries bile from the liver 

 and discharges it into the small intestine. The pancreas (sweetbread) pours 

 its secretion (pancreatic juice) into the small intestine, principally through 

 this duct. There is a vast number of small glands which line the small and 

 large intestine, and pour their respective secretions into them. 



DIGl^^STION may be briefly described as the process which dissolves food 

 and renders it capable of being taken up (absorbed) by the system. In order 

 to attain this end, the alimentary canal has to convey the food in a gradual 

 manner from front to rear. Thus, while the food is being ground by the 

 back teeth, it becomes saturated with saliva, which assists the act of swallow- 

 ing, and helps to dissolve sugar and starch. When it arrives in the stomach, 

 the gastric juice aids in dissolving the nitrogenous matter (albumin, etc.) con- 



