392 INTERNAL PARASITES. 



food between the back teeth, to be ground up. The tongue also plays a 

 large part in swallowing. The hard palate forms the roof of the month, 

 and the soft palate is the membranous 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 PHARYNX (p. 348) is a cavity common to the alimentary canal and 

 the air passages. 



THE GULLET (cesophagus) is the tube which carries food from the 

 pharynx to the stomadh. 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 fluid. 



THE LARGE INTESTINE is made up of the cascum, large colon, and 

 the small colon. The large or double colon is a wide canal which begins 

 at the c^cum and ends at the commencement of the small colon. It con- 

 sists 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 iloating 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. The 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, which is the 

 smooth and 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. 



DIGESTION 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. I&us, while the food is being ground 

 by the back teeth, it becomes saturated with saliva, which assists uie act 



