THE DUODENUM. 1645 



The first part is often egg-shaped, narrowing at the ends. Its main direction 

 is backward, slightly upward and to the right, to reach the first lumbar vertebra ; but, 

 as it is movable, its direction is somewhat variable. The gut rests above against the 

 quadrate lobe of the li\er and the neck of the gall-bladder, behind which it is free, 

 forming the lower border of the foramen of Winslow. The left side looks into the 

 lesser peritoneal cavity, and is crossed near the back by the common bile-duct. The 

 right side is chiefly against the liver and gall-bladder ; otherwise it is in contact, as 

 is the lower side, with coils of the small intestine. The lower side, moreover, rests 

 on the head of the pancreas. 



The second part descends vertically, forming an acute angle with the first. 

 It is bent so sharply that a fold of the entire thickness often projects into the gut. It 

 lies on the right side of the \-ertebral bodies beside the vena cava, and behind rests on 

 the right suprarenal capsule and kidney, being in contact also with the pelvis of the 

 latter, the renal vein, and the beginning of the ureter. The precise relations with 

 the right kidney are uncertain, owing to the variations both of that organ and of the 

 duodenum. It lies on the right against the ascending colon and on the left against 

 the head of the pancreas, which may overlap it in front. The bile-duct runs along the 

 left side and passes obliquely through the intestinal wall, to empty, in conjunction with 

 the pancreatic duct, some 10 cm. from the pylorus. 



From observations on fifty-four adult duodena (thirty-eight male, sixteen female) we have 

 found that in the great majority of duodena of both se.xes the lowest point is opposite the fourth 

 lumbiir \ertebra or the disk above or below it. In about one-quarter of the cases it is opposite 

 the third, and only some half dozen times opposite the fifth, of which cases some were probably 

 pathological. The mean of the female duodenum, in which sex the \'-shape is most frequent, 

 is a little lower than that of the male, but not strikingly so. The angle between the second 

 and the third parts in the U-form is rather less sharp than that between the first and the second. 



The third part curls around the spinal column, passing forward to its front and 

 then to the left with a slight ascent till it reaches the aorta. It crosses the vena 

 cava and has the pancreas above it, which, with the first and second parts, it tends to 

 enclose. The head of the pancreas may, however, more or less overlap the third part 

 as it does the second, and also insinuate itself behind it. In less than one-quarter of 

 the cases the third part crosses the aorta, its course being more trans\'erse than the 

 one just described. It may be connected to the aorta by areolar tissue or, especially 

 if it run only just beyond the aorta, a fold of peritoneum may intervene. 



The fourth part usually begins at an obtuse angle with the third, and ascends 

 on the front of the spine to the top of the second lumbar vertebra. In this course 

 it overlaps the aorta and usually ends either directly over it or just at its left. In 

 fifty-four observations the duodenum was on the right of the aorta until just before 

 its final flexure twenty-six times. It was wholly on the right of the aorta six times. 

 The fourth part lay in front of the aorta elex^en times and the third part actually 

 crossed it eleven times. It is clear from the above that it is exceptional for the duo- 

 denum to reach the left kidney and ureter, but it may do so when it really crosses 

 the aorta. The tail of the pancreas is behind it, as is usually a part of the left supra- 

 renal capsule. The head of the pancreas may be so developed as to overlap it, but 

 this is rare. The mesentery of the small intestine usually rises above on its front sur- 

 face and gradually crosses it to the right. It may be very nearly surrounded by 

 peritoneum, or the posterior surface may be without it. Sometimes, although rarely, 

 the last part stops short of the second lumbar. In the V-shaped duodenum the third 

 and fourth parts are in one. This form evidently is wholly to the right of the aorta, 

 except, perhaps, the very end. It sometimes ascends along the right side of the right 

 iliac artery, and then on the right or front of the aorta. The duodenum ends in a 

 sharp turn, the dnode^io-jejioial flextire. The very top of the gut at the bend is 

 suspended from the left crus of the diaphragm and from the areolar tissue about the 

 coeliac axis by the dtwdenal stispensory muscle of Treitz, a small triangular band of 

 muscular and fibrous tissue, which reaches the gut where it is uncovered by perito- 

 neum, and is said to join the layer of longitudinal muscular fibres. This band and 

 the diwdeno- hepatic ligament hold all the duodenum after the very beginning sus- 

 pended and fixed so that only the beginning is movable. It is further secured by 



