308 SPLANCHNOLOGY. 



obliquely the middle line of the abdominal floor. It measures- 

 about thirty-six inches in length, and its capacity may average six 

 gallons. It is somewhat conical in shape, and curved at its supero- 

 posterior extremity, presenting on its outer surface a number of 

 circular constrictions, and certain longitudinal muscular bands, of 

 which there are four about the middle. The superior extremity is 

 called the base or arch, and presents a convex curvature directed 

 backward, and a concave one forwards. In the concave curvature 

 the ileum terminates, and there also the large colon originates. 

 The middle part of the caecum is related with the small intes- 

 tines, the apex being free, and prolonged to the sternum. It is 

 fixed to the abdominal wall posteriorly by cellular tissue, and to 

 the origin of the colon by a double fold of peritoneum, called the 

 meso-caecum. 



The interior of the caecum presents a number of transverse 

 ridges, corresponding to the external transverse constrictions. Two 

 orifices, placed one above the other, are found in its concave 

 curvature; the inferior one marks the termination of the ileum, 

 and is guarded by the ileo-coecal valve, which is formed by a 

 doubling of the mucous membrane, within which is a band of 

 muscular fibres. The superior opening communicates with the 

 colon. The caecum has three coats, serous, muscular, and mucous, 

 the latter being thicker than that of the small intestines, and 

 having neither Brunner's glands nor Peyer's patches. The folli- 

 cles of Lieberkiihn, solitary glands, and a few scattered villi are 

 however present. 



GREAT COLON. 



The great or double colon originates from the caecum, and ter- 

 minates near its origin in an abrupt contraction, whence arises 

 the floating colon. Taken out of the abdomen, it appears as a 

 voluminous tube, with successive dilated and constricted portions; 

 like the caecum, it is marked throughout by longitudinal bands 

 and transverse furrows. It measures, on an average, from nine to 

 eleven feet in length, and sometimes has the capacity of eighteen 

 gallons. It is doubled on itself, forming two branches of equal 

 length, placed one on the other, and so disposed that the terminal 

 end is near the origin. When in situ, the doubled portion 

 forms a curve whose convexity is directed forwards, and corre- 

 sponds to the walls of the abdomen, thus forming four divisions, 

 a right and left being above, and a right and left below, with 



