DIGESTION 229 



does an innocent or benign organism acquire the power to excite a specific 

 form of disease under any method of cultivation which has yet been 

 devised. 



The specific organisms which are found in contagious disease to which 

 the horse is subject, are referred to and illustrated in the description of 

 those affections. 



DIGESTION 

 THE ALIMENTARY CANAL AND ITS APPENDAGES 



The alimentary canal is a tube which, commencing at the mouth, is 

 continued by means of the pharynx and oesophagus to the stomach, where 

 it undergoes considerable enlargement. It then contracts again to form 

 the small intestine, which is a long and coiled cylinder. This is suc- 

 ceeded by the large intestine, which terminates in the rectum with its 

 outlet, the anus. The total length of the alimentary canal in the horse 

 is about ten times the length of the body, and hence may be estimated 

 at 100 feet, which may be thus apportioned: 



.Mouth and pharynx 1 foot. 



Oesophagus 3 feet. 



Stomach ... ... ... ... ... ... ... 2 ,, 



Small intestine ... 72 „ 



/"Caecum ... ... 3 



Large intestine °°!° n ' lar S e , ^ 



Colon, small ... ... 10 



I Rectum ... ... 1. 



The appendages of the alimentary canal are the lips, teeth, and salivary 

 glands in connection with the mouth, and the liver and pancreas in con- 

 nection with the small intestine. Each of these parts is deserving of a 

 short description. 



The lips are fleshy, movable organs, possessing a high degree of 

 sensibility, and adapted for the prehension of food and for its retention 

 within the cavity of the mouth during mastication. Externally they have 

 a covering of hairy skin, some of the hairs being very large and long, and 

 probably possessing an acute sense of touch; internally the lips are lined 

 by mucous membrane, and present the openings of the ducts of many small 

 salivary glands. 



The teeth, more fully described elsewhere, are hard, bony organs, of 

 immense importance in cutting, bruising, and breaking down the food. 



