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CHAPTER XXV. 



OF INTESTINAL DIGESTION. ANATOMY OF THE INTESTINAL CANAL IN 



MAN AND VERTEBRATA. THE MUCOUS MEMBRANE OF THE INTES- 

 TINE. ITS FOLDS AND VILLI. ITS GLANDS. DIGESTION IN THE 



SMALL INTESTINE. FLUIDS POURED INTO THE SMALL INTESTINE. 



THE PANCREATIC FLUID. THE BILE. THEIR INFLUENCE. 



DIGESTION IN THE LARGE INTESTINE. DEFECATION. 



Anatomy of the Intestinal Canal. The intestinal canal commences 

 at the pylorus and terminates at the anus. It exhibits a very 

 obvious subdivision into two portions: a narrower and much 

 longer portion, disposed in numerous coils and convolutions, which is 

 called the small intestine (intestinam tenue) ; and a much wider 

 but shorter portion, the large intestine (intestinum crassum) . The 

 length of the whole intestinal canal in the adult is between thirty 

 and forty feet, or about six times that of the body : the small 

 intestine forms five-sixths of this. 



There is a very distinct natural demarcation between these two 

 portions of the intestinal canal ; the large intestine commences by a 

 dilated cul-de-sac, which communicates on its inner side with the 

 small intestine. This portion, which is the widest part of the large 

 intestine, is lodged in the right iliac fossa; it constitutes the com- 

 mencement or the head of the colon, and as it forms a blind extre- 

 mity or cul-de-sac beyond the junction of the small intestine with it, 

 it is named caput ccecum coli, or commonly caecum. Connected with 

 it is a remarkable appendix, which proceeds from its inner and 

 posterior part, and hangs down into the pelvis in a slightly curved 

 form, which gives it the appearance of a worm (lumbricus) , and 

 receiving support from a small fold of peritoneum. This is called 

 the appendix cceci vermiformis. It is a small process from the 

 caecum, hollow, cylindrical, in size rather larger than a goose-quill, 

 about three inches long, and ending in a blind extremity which lies 

 free in the pelvis, but having a free communication with the caecum 

 where it is attached to that intestine. The large intestine com- 

 mencing at this part ascends from the right iliac fossa, through the 

 right lumbar region, as high as the concave surface of the liver; 



