282 THE HORSE. 



are not mixed with the food, the nutrition of the body will be 

 imperfectly carried on, and its health will suffer. But if the ele- 

 ment of bile and urine are retained in the blood, not only is the 

 system upset, but absolute death is produced in severe cases. 

 Hence it follows, that attention to the state of the organs of 

 depuration, or excretion, is of more importance even to those of 

 secretion, using these terms in the sense explained in the last para- 

 graph. The chief organs of depuration are the lungs, which re- 

 move carbon from the blood ; the liver, which secretes the bile ; 

 the kidneys which get rid of the urea ; and the skin, which relieves 

 it of its superfluous watery and some small proportion of its solid 

 particles. Experiment shows that the retention of carbon, or urea, 

 in the blood is speedily followed by death ; while the non-secretion 

 of bile, if entire, poisons the system; and in milder cases, its 

 absence from the alimentary canal interferes with the due elabora- 

 tion of the chyle. 



THE STOMACH. 



THE STOMACH is situated on the left side of the abdominal 

 cavity, immediately behind the diaphragm. It resembles in shape 

 the bag of the Scotch bag-pipes, having two openings, two curva- 

 tures (a lesser and a greater), two surfaces, and two sacs, which 

 are generally divided by a constriction. Its volume varies with 

 its contents, but in the horse of average size it will not contain 

 more than three gallons, while the stomach of man, whose weight 

 is only one-eighth that of the horse, holds three quarts. 



THE INTESTINES. 



THE INTESTINES, large and small, constitute a hollow tube, 

 very variable in diameter, and measuring from eighty to ninety feet 

 in length in an average-sized horse. They extend from the stomach 

 to the anus ; and though nature has only divided them into two 

 portions, the small and large, yet anatomists have subdivided each 

 of these into three more, namely, duodenum, jejunum, and ileum 

 co3cum, colon, and rectum. 



THE SMALL INTESTINES are about seventy feet long, and vary 

 from an inch to an inch and a half in diameter, except at their 

 commencement, where there is a considerable dilatation, forming 

 a sort of ventriculus or lesser stomach. They are gathered up 

 into folds, in consequence of the mesentery, which attaches them 

 to the superior walls of the abdomen, being of very limited extent 

 as compared with their length ; and thus they may be described 

 as presenting two curves, a lesser mesenteric curvature, and an 

 outer or free one covered by the peritoneum. The outer layer of 

 the muscular coat consists only of a few and scattered fibres, while 

 the inner one is circular in its arrangement, and though thin as 



