THE INTESTINES. 203 



rt The commencement of the small intestines. The ducts which convey the hile and thy 



secretion from the pancreas are seen entering a little below. 

 h b Tlie convolutions or windings of the small intestmes. 

 c A portion of the mesentery. 

 d The small intestines terminating in the coecum. 

 e The ccecum or blind gut, with the bands running along it, puckering and dividing it 



into numerous cells. 

 / The beginning of the colon. 



fj The continuation and expansion of the colon, divided like the coecum into cells, 

 h The termination of the colon in the rectum. 

 i Tlie termination of the rectum at the anus. 



The intestines of a full grown horse are not less than ninety feet in 

 length. The length of the intestines in different animals depends on the 

 nature of the food. The nutritive matter is with much more difficulty ex- 

 tracted from vegetable than animal substances, therefore the alimentary canal 

 is large, long, and complicated, in those which, like the horse, are fed on 

 herbs alone. They are divided into the small and large intestines ; the 

 former of which occupy about sixty-six feet, and the latter twenty-four. 

 The intestines, like the stomach, are composed of three coats. The outer 

 one consists of the peritoneum, that membrane which we have already 

 described as covering the contents of the belly. By means of this coat the 

 bowels are confined in their proper situations ; and, this membrane being 

 smooth and moist, all friction and concussion are a.voided. Did the bowels 

 float loosely in the belly they would be subject to constant entanglement 

 and injury amid the rapid and violent motions of the horse. 



The middle coat, like that of the stomach, is muscular, and composed of 

 two layers of fibres, one running longitudinally, and the other circularly ; 

 and by means of these muscles, which are continually contracting and re- 

 laxing from the upper part downward, the food is forced along the bowels. 

 The inner coat is the mucous or villous ; — mucous, because it abounds 

 with small glands which pour out a mucous fluid to lubricate the passage 

 and defend it from irritating or acrimonious substances ; and villous from 

 its soft velvet feel. This coat is crowded with innumerable little mouths, 

 which are the commencement of minute vessels, by which the nutritive 

 part of the food is taken up ; and these vessels, uniting and passing over 

 the mesentery, carry this nutritive matter to a receptacle for it, whence it is 

 conveyed into the circulation and distributed to every part. 



The intestines are more particularly retained in their places by the ?7ze- 

 seniery, c, (middle of the intestines,) which is a doubling of the peritoneum, 

 including the intestine in its bottom, and likewise inclosing between its 

 folds the' arteries and veins, and nerves, and the vessels which convey the 

 nutriment from the intestines to the circulation. The mesentery has some- 

 what the appearance of an expanded fan, and all these things ramifying 

 between its transparent folds, give it a beautiful appearance. 



The first of the small intestines is the Duodenum, a, so called be- 

 cause, in the human subject, it is about twelve inches long. In the horse it 

 is nearly two feet in length. It is the largest in circumference of all the small 

 intestines. It receives the food converted into chyme by the digestive power 

 of the stomach, which in it undergoes another and very important change ; 

 a portion of it is converted into chyle. It is mixed with the bile and the 

 secretion from the pancreas, which enter about five inches down the intes- 

 tine. The bile seems to be the principal ag^nt in this change ; no sooner 

 does it mingle with the chyme, than the fluid begins lobe separated into two 

 distinct ingredients ; a white thick liquid, termed chyle, and containing the 



