ABDOMEN AND PELVIS 471 



anterior caecal and the appendicular and recurring iliac arteries, 

 and also a band of muscle passing from the base of the appendix 

 to the ileum. There are thus formed three 



Folds (plicae). 



(a) Mesentericocaecal fold (plica mesentericocaecalis), which con- 



tains the short anterior caecal artery. 



(b) Meso-appendix (mesentericum processus vermiformis), in which 



the appendicular artery runs. 



(c) Ileocaecal or ileo-appendicular fold (plica ileocaecalis or plica ileo- 



appendicularis) , containing the muscular band passing from the 

 base of the appendix to the ileum and the recurring ileal branch 

 of the appendicular artery. This plica is often spoken of as the 

 " bloodless fold of Treves." 

 These three plicae form two fossae. 



Fossae. (See Cunningham, pp. 1030, 1031; Poirier et Charpy, pp. 338- 

 340.) 



(a) Superior ileocaecal recess (recessus ileocaecalis superior), situated 



behind the plica mesentericocaecalis. This fossa and fold corre- 

 spond to the ileocolic of Cunningham. It. is well developed in 

 the new-born, but is less distinct in the adult. Increase in the 

 diameters of the caecum and deposition of fat within the plica 

 account for the diminution in size. 



(b) Inferior ileocaecal recess or ileo-appendicular fossa (recessus ileo- 



caecalis inferior). This is the ileocaecal fossa of Cunningham. 

 If the appendix is drawn downward and the finger passed along 

 the lower border of the terminal part of the ileum towards the 

 caecum, it will generally enter a fossa situated in the angle 

 between the ileum and the caecum. The fold bounding this fossa 

 in front is the " bloodless fold of Treves," or plica ileocaecalis ; 

 that behind, the meso-appendix, or mesenteriolum processus ver- 

 miformis. 



Turn the caecum and adjacent parts of the ileum upward and 

 expose the following : 



Folds (plicae). 



(a) Parietocaecal fold (plica parietocaecalis) , extending from the iliac 



fossa or lumbar region to the external wall of the caecum or 

 colon ascendens. Note the general shape and attachments of this 

 fold. Does it contain vessels? Between what vessels do they 

 establish an anastomosis? (Vide Poirier et Charpy, t. iv., 340.) 



(b) Mesentericoparietal fold (plica mesentericoparietalis) . This fold 



represents not only the attachment of the mesentery to the iliac 

 fossa, but also its prolongation below along the posterior abdomi- 

 nal wall into the pelvic cavity. Is this fold ever prolonged as 

 far downward as the openings of the femoral and inguinal 

 canals? 

 Fossae or recesses. 



(a) Retrocaecal fossa (recessus retrocaecalis) . 



Determine accurately the boundaries, depth, breadth, etc., of 



