404 THE COMPLETE GRAZIER. BOOK in. 



teeth ; and the pre-maxillaries, lodging the upper incisors. The roof of 

 the mouth is occupied hy the palatal bones, which separate the mouth 

 from the nasal cavities. The lower jaw or mandible consists of a pair 

 of flat bones (right ramus and left ramus), united in front at the 

 symphysis rami, and each articulating by means of its condyle with the 

 squamosal bone of the skull. 



Various details in the external conformation of the horse are 

 indicated in fig. 93, which may be usefully compared with the diagram 

 of the skeleton (fig. 90). 



THE ALIMENTARY CANAL. The digestive tract consists of a tube of 

 varying diameter, commencing at the mouth, and ending at the anal 

 aperture. The course taken by the food is: mouth, pharynx (a large 

 chamber at the back of the mouth), oesophagus or gullet, stomach, 

 small intestine, large intestine, rectum. The food is comminuted in 

 the mouth, the lips, cheeks, tongue, hard palate, soft palate, and teeth, 

 all taking their share in the work, whilst the salivary glands (the 

 parotid, submaxillary, sublingual, and molar or buccal) simultaneously 

 pour out their juices. Mixed with abundant saliva the food is trans- 

 ferred to the pharynx, whence it passes into the gullet, which is merely 

 a tube along which the food can travel to the stomach, this last-named 

 organ being a dilatation of the alimentary canal. Here the true work 

 of digestion begins, the gastric juice, secreted by the peptic glands 

 in the internal lining of the stomach, effecting the solution of the 

 nitrogenous ingredients (proteids) of the food, which are carried away 

 as dissolved peptones by the blood circulating in the delicate blood 

 capillaries of the wall of the stomach. 



Passing through the pyloric aperture the alimentary mass emerges 

 from the stomach into the small intestine, where other digestive 

 juices, notably that of the liver (the bile), and that of the pancreas 

 or sweetbread (the pancreatic juice), further attack and disintegrate the 

 food. The physiological nature of these processes is discussed in the 

 chapter on the Secretion of Milk (pp. 271 to 295). , 



The diagram (fig. 94) indicates the "regions" of the abdomen as 

 conventionally marked out on the inferior face of the abdominal wall, 

 viewed from below. 



The stomach of the horse is a membranous muscular sac possessing 

 an average capacity of 3 to 3| gallons, though it varies according to the 

 size of the animal, the breed, and the food. It is relatively larger in 

 common-bred horses, and in the ass and mule. Its average weight 

 when empty is 3 to 4 Ib. Elongated laterally, and curved on itself, it 

 is often constricted in the middle. Interiorly the left half is lined by 

 membrane like that of the gullet, and contains no peptic glands. The 

 right-hand half of the inside is, on the contrary, thick, wrinkled, 

 spongy, very vascular, and richly beset with the glands which secrete 

 the gastric juice. Hence, it is only the right hand side of the interior 

 of the horse's stomach which has any true digestive power ; the 

 transition from the functionless left to the functional right is indicated 

 internally by a sharply-marked ridge with which an external constric- 

 tion corresponds. In the human stomach the whole of the internal 



