ABDOMEN AND PELVIS 469 



its relation to the duodenum, the head of the pancreas, and the 

 duodenojejunal angle. What is the length of this mesocolon? 

 Does it readily permit of displacement of the colon ? Note that the 

 peritoneal relations of the first part of the transverse mesocolon 

 depend somewhat upon the position and size of the liver. (Vide 

 Cunningham, p. 1033.) 



(c) Descending mesocolon (mesocolon descendens). The descending colon 



is fixed in eighty-five per cent, of the cases ( Jonnesco and Charpy) ; 

 in sixty-four per cent. (Treves). The disappearance of the primi- 

 tive mesocolon descendens is accounted for by Toldt's theory. De- 

 termine the relation of the fascia remaining to the left kidney and 

 ureter. Determine with accuracy the relation of the left kidney 

 to the descending colon. Do you find any paracolic fossae (recessus 

 paracolici) ? 



(d) Sigmoid mesocolon (mesocolon sigmoideum). Note its general direc- 



tions and relations. (Vide Cunningham, p. 1035.) The length of 

 this mesocolon bears a relation to the frequent torsion of the bowel 

 (volvulus) occurring here. Does the length of this part of the in- 

 testine differ in carnivora, herbivora, and omnivora? Where does 

 the mesocolon sigmoideum end? 



Mesorectum. 



Where does the mesorectum begin? How is it related to the 

 sacral vertebrae ? How far is it attached to the rectum ? 



After having made a careful study of these different perito- 

 neal folds, the student should turn the omentum and transverse 

 colon up on to the thoracic wall and proceed to the study of 



Peritoneal Fossae about the Duodenojejunal Angle. (Vide Fig. 247 ; 

 Cunningham, p. 1018; Poirier et Charpy, t. iv. pp. 265-267.) 



(a) Inferior duodenal fossa (fossa duodenalis inferior). How frequently 



is this fossa present ? Determine its relation to the terminal portion 

 of the duodenum and to the vertebrae. Is this fossa vascular? 

 What is the inferior duodenal plica (plica duodenalis inferior) ? 

 Determine depth and width of this fossa, comparing it with fossae 

 found in other subjects. 



(b) Superior duodenal fossa (fossa duodenalis superior). This fossa is 



found in about fifty per cent, of the cases, occurring less constantly 

 than the preceding. What relation does it bear, if present, to the 

 second lumbar vertebra and the body of the pancreas? What is 

 the superior duodenal plica (plica duodenalis superior) ? Is this 

 fossa vascular? If so, determine what vessels course in the plica. 

 The two fossae frequently occur together. If both are present in 

 your subject, compare as to depth, width, vascular relations, etc. 



(c) Duodenojejunal fossa (fossa duodenojejunalis of Jonnesco). This 



fossa occurs in about twenty per cent, of the cases and is never 

 coincident with the other fossae found at this flexura. Determine 

 the relation that this fossa bears to the aorta, ihe left kidney, and 

 the left renal vein. What are the plica duodenojejunalis dextra 

 and sinistra? 



