THE PERITONEUM. 



997 



formerly made the descending mesocolon. On the right side the subccecal fossa 

 is made in a similar way. 



" The Psoas minor muscle can raise the peritoneum into a fold by the spread- 

 in out of its tendon of insertion into the fascia iliaca ; at the side of this a peri- 



Inter- 

 sigmoid 

 fossa. 



Spermatic 



MttEb 



FIG. 620. Fossa-intersigmoidea. Sigmoid flexure of a new-born, drawn upward. (Henle). 



toneal fossa may exist which in some cases receives a part of the descending 

 colon." Biesiadecki, who described it, gave it the naine/ossa iliaco-subfascialis. 

 This fossa, of course, is of slight importance. 



Pericaecal Fossae. 



At least three fossae are to be found in the csecal region. There is no agree- 

 ment upon their frequency and nomenclature. Just above the ileo-colic junction 

 between the end of the ileum and ascending colon, bounded in front by an ileo- 

 colic fold may be the ileo-colic fossa, also called superior ileo-ccecal. (Luschka.) 



It is just where the mesentery changes into the peritoneal coat of the ascend- 

 ing colon. It is smaller and less constant than the next. 



Underneath the ileum, between it and the caecum, is the ileo-ccecal fossa, which 

 may be called the inferior ileo-ccecal, and has been described as the subcaecal. It 

 lies between two definite folds of peritoneum, the formation of which requires 

 explanation. Originally in the human foetus there were three folds passing 

 between the contiguous surfaces of the ileum and caecum. These are normal 

 in the spider monkey (Fig. 621). 



They are called anterior vascular, posterior vascular, and intermediate non- 



i ilar foil*. In the human subject the anterior vascular and the middle non- 

 vascular folds unite on the caecum, but do not descend upon the appendix ; the 

 posterior vascular fold with its contained posterior ileo-caecal artery passes to the 

 appendix and forms its mesentery. The space left between this fold behind and 

 the middle non-vascular fold in front is the ileo-caecal fossa (Fig. 622). 



The subccecal fossa is directly behind the crecurn ; it is really post-caecal. Its 

 fundus may pass up behind the ascending colon, i. e. the coecuui in descending 



