214 A MANUAL OF VETERINARY PHYSIOLOGY 



which the chyme passes through the small intestines varies with 

 the nature of the food, and the frequency with which the horse 

 is fed. Ellenberger says it reaches the caecum six hours after 

 feeding, but has not entirely passed into this bowel for twelve or 

 even twenty hours ; we have known it reach the caecum in four 

 hours. 



In the small intestines the chyme meets with the bile and 

 pancreatic juice ; the action of these on food will be described 

 in the chapter dealing with the liver and pancreas. The absorp- 

 tion of chyle, and its elaboration before reaching the blood, are 

 points which must be reserved for the chapter on ' Absorption.' 



Large Intestines. 



There can be no doubt that in solipeds digestion in the large 

 intestines is a very important process ; at least, we judge so 

 from the fact of their enormous development. In many respects 

 they present a considerable contrast to the small intestines ; for 

 instance, they are always found filled with ingesta, the contents 

 are more solid, the material lies a considerable time in them, and 

 there are no juices other than the succus entericus poured into the 

 bowel. These are conditions exactly the reverse of those found 

 in the small intestines. The bowels which are spoken of as the 

 large intestines are the caecum, double and single colon, and the 

 rectum. 



The Caecum has been described by Ellenberger as a second 

 stomach ; its enormous capacity and fantastic shape have always 

 rendered it an intestine of considerable interest (Fig. 73). To 

 our mind its most remarkable feature is that it is a bag, the 

 openings into and out of which are both found at the upper part 

 close together ; the exit, strange to say, is above the inlet, and the 

 contents have to work against gravity in order to obtain an entry 

 into the next intestine, the double colon. This is brought about 

 by the four muscular bands on the caecum (Fig. 74) , which shorten 

 the bowel, forcing the contents upwards towards the ' crook.' 

 The ileum being closed, the only available outlet is into the colon 

 (Fig. 75)- 



Several questions suggest themselves regarding the communi- 

 cation between the large and small intestines. It is certain that 

 in order to get from the ileum into the colon everything must pass 

 into or, at any rate, through the caecum, yet we feel sure that 

 material does not remain there long. Is it possible that the 

 openings of the ileum .and colon might be brought together so 

 that material may pass directly from one into the other ? 

 Nothing is returned into the ileum from the caecum ; there must 

 be, in consequence, a sphincter keeping the ileum closed, for 



