22O Anatomy Applied to Medicine and Surgery. 



denum has the peritoneum only ir front, while to its left 

 is the head of the pancreas which moulds itself to the 

 sKape of the bowel in this situation. In the U-shaped 

 duodenum the transverse part is between two and three 

 inches long and passes almost transversely from right to 

 left to end in the ascending portion, which is about two 

 inches in length, whereas, in the V-shaped duodenum, 

 there is no transverse portion. Relations of the trans- 

 verse portion when present : Above, the head of the pan- 

 creas and the superior mesenteric vessels ; in front, the root 

 of the mesentery and the superior mesenteric vessels; be- 

 hind, the vena cava, the aorta, the crura of the diaphragm 

 and the third lumbar vertebra. The fourth or second as- 

 cending portion terminates at the side of the upper border 

 of the second lumbar vertebra, where it turns abruptly 

 forward to join the jejunum forming the duodeno-jeju- 

 nal angle. Relations : It is covered by peritoneum on the 

 front, and, to some extent, on the sides also. It rests on 

 the psoas muscle and left renal vein and has in front of it 

 the transverse colon which separates it from the stomach, 

 though at times the latter organ itself lies in front of it. 

 Internally, are the aorta and the neck of the pancreas. 

 This ascending portion of the duodenum is supported and 

 held in its place by a fibrous band called the "muscularis 

 suspensorius of Trietz," which runs from the side of the 

 left crus to this portion and even beyond it, according to 

 Lockwood. This suspensory muscle passes beyond the 

 duodenum, between the layers of the mesentery, and sup- 

 ports the rest of the small intestine and the mesentery as 

 well as the duodenum. The arrangement of the periton- 

 eum in connection with this part of the duodenum is such, 

 that a pouch is formed, funnel-shaped and with mouth up- 

 wards, by a fold running from the front of the duodenum 

 to the parietal peritoneum. This pouch admits the tip of 



