THE INTESTINES. 483 



two of which are prolonged to the floating colon. The transverse folds formed 

 by these flat bands are but faintly marked towards the pelvic curvature, and are 

 altogether absent in the narrow portion succeeding it ; it is only in the whole 

 extent of the first dilatation that they are deepest and most numerous. 



Liternal surface. — This is exactly like that of the caecum. 



Structure. — The serous membrane envelops the whole of the colon, except in 

 those places where it comes in contact with itself or with other viscera. So it 

 iiappens that the peritoneum, in passing from the sublumbar region to the last 

 portion of the colon, does not cover the surface, which adheres by connective 

 tissue to the inferior aspect of the pancreas and csecum ; neither, in being carried 

 from one branch of the colic flexure to the other, does it envelop their opposed 

 sides, except at the pelvic flexure, where it forms the meso-colon. 



The muscular tunic does not differ in its arrangement from that of the 

 caecum ; neither does the mucous membrane. The arteries emanate from the 

 great mesenteric ; they are the two colic arteries. The two satellite veins soon 

 form a single trunk, which enters the vena portae. The lymphatics empty them- 

 selves into Pecquet's reservoir. The nerves emerge from the great mesenteric 

 plexus. 



The Small, Single, or Floating Colon (Fig. 282). — This is a sacculated 

 tube, which succeeds the large colon, and is terminated in the pelvic cavity 

 by the rectum. 



Length — Form — Course — Relations. — It is about 10 feet in length, and is 

 arranged in a similar manner to the small intestine, except that it is double the 

 size of that viscus, is regularly sacculated on its surface, and is provided with 

 two wide and thick longitudinal bands, one on the side of its great, the other on 

 its small, flexure. Arising from the terminal extremity of the large colon, to the 

 left of the cfficum, where it is related to the termination of the duodenum, and 

 where it receives the insertion of the great omentum, this intestine is lodged in 

 the left flank, forming folds which are mixed with the convolutions of the small 

 intestine. It afterwards passes into the pelvic cavity, to be directly continued by 

 the rectum. 



Mode of attachment. — Floating like the small intestine, the small colon is 

 suspended by a serous layer, exactly similar to the mesentery proper, though 

 wider, and named the colic mesentery. This mesentery is detached from the 

 sublumbar region, not from around a central point, but from a line extending 

 from the great mesenteric artery to the interior of the pelvic cavity. It is 

 narrower at its extremities than in its central portion. 



Interior. — The interior of the floating colon shows valvular folds, analogous 

 to those of the csecum and large colon. It is in the intervals between these that 

 the fgecal matters are moulded into balls. 



Structure. — The serous membrane is without special interest, and the 

 muscular tunic is similar to that of the large colon. The mucous membrane is 

 also the same. These membranes receive their blood by the small — and a 

 branch of the gi'eat — ynesenteric artery. A venous trunk, passing between the 

 layers of peritoneum forming the mesentery, carries back the blood to the vena 

 portae. The lymphatics are nearly as fine and numerous as those of the small 

 intestine ; they enter the same confluent — the reservoir of Pecquet. 



Functions of the Colon. — In this intestine is accomplished the absorption 

 of fluids, and of soluble alible matters. When the alimentary mass arrives in 

 the small colon, deprived of its assimilable principles and charged with excretory 



