THE INTESTINES. 



317 



the rectum. The first of tli em is the ctecwn. (bHnd gaat), (e), — it has but one 



opening into it, consequently everything that passes into it, having reached 



the blind or closed end, must return, in 



order to escape. It is not a continuation 



of the ileum, but the ileum pierces the 



head of it, as it were, at right angles 



(d), and projects some way into it, 



and has a valve — the valvula coli — 



at its extremity, so that the food that 



has passed from the small intestines into 



the larger cannot again be returned. 



Along the outside of the caecum run 



three strong bands, each of them shorter 



than that intestine, and thus puckering 



it up, and forming it into three sets 



of cells, as shown in the accompanying x^; ^^~:z:^^~^^^^^^y^ 



side cut. 



That portion of the food which has not been taken up by the lacteals or 

 absorbent vessels of the small intestines passes through this valvular 

 opening of the ileum, and a part of it enters the colon, while the remainder 

 flows into the caecum. Then, from this being a blind pouch, and from the 

 cellular structure of this pouch, the food must be detained in it a very long 

 time ; and in order that, during this detention, all the nutriment may be 

 extracted, the caecum and its cells are largely supplied with blood-vessels 

 and absorbents. It is principally the fluid part of the food that seems to 

 enter the caecum. A horse will drink at one time a great deal more than 

 his stomach will contain ; or even if he drinks a less quantity, it remains 

 not in the stomach or small intestines, but passes on to the caecum, and 

 there is retained, as in a reservoir, to supply the wants of the system. In 

 his state of servitude the horse does not often drink more than twice or 

 thrice in a day, and the food of the stabled horse being chiefly dry, this 

 tvater stomach is most useful to him. The ctecum will hold four gallons. 



The colon is an intestine of exceedingly large dimensions, and is capable 

 of containing no less than twelve gallons of liquid or pulpy food. At its 

 union with the caecum and the ileum, although larger than the latter in- 

 testine (/), it is of comparatively small bulk ; but it soon swells out to an 

 enormous extent. It has likewise, in the greater part of its course, three 

 bands like the caecum, which also divide it, internally, into the same 

 description of cells. The intention of this is evident,— to retard the 

 progress of the food, and to give a more extensive surface on which the 

 vessels of the lacteals may open ; and therefore, in the colon, all the chyle 

 is finally separated and taken up. This intestine is of considerable length; 

 it completely traverses the diameter of the abdominal cavity, and is then 

 reflected on itself, and retraverses the same space. When this is nearly 

 accomplished, the construction of the colon is somewhat changed: — we find 

 but two bands towards the rectum, and these not puckering the intestine 

 so much, or forming such numerous or deep cells. The food does not 

 require to be much longer detained, and the mechanism for detaining it 

 is gi'adually disappeaiing. The blood-vessels and absorbents are likewise 

 rapidly diminishing. The colon, also, once more contracts in size, and the 

 chyle having been all absorbed, the remaining mass, being of a harder 

 consistence, is moulded into pellets or balls in its passage through these 

 shallower cells. 



At the termination of the colon, the rectum (straight gut) commences. 

 It is smaller in circumference and capacity than the colon, although it will 

 contain at least three gallons of water. It serves as a reseiwoir for the 



