INTESTINES IN THE HORSE. 55 



cular coat of the organ, so as to give place to an inner layer of 

 the mass, and it appears in the mean time to undergo a kind 

 of circulation, so that the interior parts are in succession 

 brought into contact with the secreting surface of the inner 

 coat. In this manner the whole mass is gradually formed into 

 chyme, and then expelled by a more powerful movement into 

 the duodenum, the resistance of the pyloric valve being over- 

 come. 



Intestines in the Horse. It was already said that the intes- 

 tines of the horse, as being a purely vegetable feeder, are of 

 extreme length (p. 5). The intestines of the horse are about 

 ninety feet long, or between eight and nine times the length 

 of his body. The great intestines make but a small part of 

 this great length. The duodenum, the jejunum, and the 

 ilium are the three divisions of the small intestines ; while the 

 caecum, the colon, and the rectum are the three parts of the 

 great intestines. The coats of the intestines are three, as 

 in the stomach namely, an exterior serous derived from the 

 peritoneum ; a middle muscular, composed of both circular and 

 longitudinal fibres; and the internal mucous. As before 

 noticed (p. 36), while the peritoneum or serous lining mem- 

 brane of the abdominal cavity affords an outer covering to 

 the intestines, it also forms the remarkable folds between 

 the laminae of which the vessels and nerves of the intes- 

 tines are supported, and by which the intestines, some in a 

 much less degree, others in a greater degree, are retained in 

 their place. There are certain parts of the intestines that are 

 less completely covered by the peritoneal coat than the rest 

 namely, the duodenum, the caecum, and the rectum ; and these 

 several parts have a more fixed position than the other parts 

 in general. This will be easily understood by a familiar com- 

 parison. The intestines, generally, are like the arm placed in 

 a sling hung from the neck, the handkerchief enveloping the 



