THE ILEO-COLIC JUNCTION. 



325 



has an aperture of communication with the intestine (d). In struc- 

 ture it resembles the rest of the colon, except that the longitudinal 

 muscular bands coalesce upon it. Its mucous membrane contains a 

 great amount of adenoid tissue. 



Dissection. To examine the interior of the dried specimen of 

 the caecum, and the valve between it and the small intestine, the 

 following cuts should be made in 

 it : One oval piece is to be taken 

 from the upper aspect of the ileum 

 near its termination ; and another 

 from the side of the caecum, opposite 

 the entrance of the small intestine. 



lleo-colic valve (fig. 120). This valve 

 is situate at the entrance of the ileum 

 into the large bowel. It is composed 

 of two pieces, which project into the 

 interior of the colon and bound a 

 narrow, nearly transverse, aperture of 

 communication between the two parts 

 of the intestinal canal. 



The upper piece of the valve, ileo- 

 colic (e), projects horizontally into the 

 large intestine, opposite the junction 

 of the ileum with the colon. And 

 the lower piece, ileo-ccecal (/), which 

 is the larger of the two, has a nearly 

 vertical direction between the ileum 

 and the caecum. At each extremity 

 of the opening the pieces of the valve 

 are blended together ; and the re- 

 sulting prominence (g) extends trans- 

 versely on the front and back of the 

 intestine, forming the frcena or reti- 

 nae itla of the valve. 



The size of the opening is altered 

 by the distension of the intestine ; 

 for when the retinacula of the valve 

 are stretched the folds bounding the 

 aperture are approximated, and may 

 be made to touch. 



Each piece of the valve is formed 

 by circular muscular fibres of the 



intestinal tube, covered by mucous membrane and submucous tissue ; 

 and the ileum projects into the interior of the caecum as if it 

 were thrust obliquely through the wall of the csecum, after being 

 deprived of its peritoneal coat and the layer of longitudinal fibres. 

 This construction is easily seen on a fresh specimen by dividing the 

 peritoneum and the longitudinal fibres, and gently drawing out the 

 ileum from the caecum. 



One ileo- 

 colic ; 



the other 

 ileo-csecal ; 



these are 

 joined at 

 the ends, 



FIG. 120. INTERIOR OF THE 



C^CUM, DRIED AND LAID 

 OPEN. 



a. Caecum. 



b. Small intestine. 



c. Vermiform appendix, and 

 d, its aperture. 



e. lleo-colic piece of the valve 

 at the junction of the small 

 intestine. 



/. Ileo-csecal piece of the 

 valve. 



g. Retinaculum of the valve 

 on each side. 



and form 

 frsena. 



Opening in 

 the valve. 



The valve a 

 prolonga- 

 tion of the 

 wall of the 

 gut. 



