44S SCHl'LTE, SEI WHALE. 



indeed upon its distal slope, is situated the flaring pylorus. This projects strongly into the 

 duodenum. The fourth compartment is thicker walled than the stomach elsewhere save at the 

 fundus of the first. Its lumen diminishes rapidly towards the pylorus. In its widest portion 

 it is smooth internally, but as it contracts it becomes marked with slight longitudinal ridges 

 and sulci which are prolonged upon the projecting pylorus to its edge. In length this compart- 

 ment measures 8 mm., in maximum diameter 6 mm. Its greatest lumen is 3 mm. which dimin- 

 ishes to less than 1 mm. just before the pylorus is reached. 



Duodenum. Four portions may be distinguished, the ampulla, descending, transverse, 

 and ascending duodenum. The ampulla is a pyriform dilatation, attaining its maximum diam- 

 eter a little distad of the pyloric sulcus and more gradually diminishing subsides to the dimen- 

 sions of the rest of the duodenum at the sharp angle where it joins the descending portion. Its 

 axis is directed dorsad, rostrad, and slightly to the left, continuing the direction of the terminal 

 portion of the fourth gastric compartment. It has a length of 7 mm., a maximum lumen of 

 2.5 mm., which at its junction with the descending duodenum is reduced to 1 mm. Its walls are 

 thickest at the pylorus and diminished in strength distad. The mucous surface shows no folds 

 but is beset with numerous conical to finger-shaped villi. The ampulla rostrad and on the left is 

 in relation with the horizontal portion of the pancreas and is crossed dorsad and to the right 

 of this by the portal vein and hepatic artery on their way to the liver. On the right it is free 

 and covered by peritoneum, while caudad it is in peritoneal contact with the descending duo- 

 denum. 



The remainder of the duodenum describes a typical loop about the root of the mesentery. 

 It is U-shaped with a tendency to angulation at the junction of its descending and transverse 

 portions. The loop is occupied by the vertical portion of the pancreas, leaving a broad longi- 

 tudinal space to the left for the large superior mesenteric artery and vein. The whole descend- 

 ing duodenum and the transverse, as far as these vessels, are free and covered by peritoneum 

 dorsally, so that only the curved termination of the transverse and the ascending portion have 

 become adherent to the parietes. The degree of anchorage of the duodenum is thus seen to be 

 small and limited to the portions to the left of the median line. The descending duodenum runs 

 caudad, distinctly ventrad and slightly to the right, being closely applied to the ampulla and 

 pyloric extremity of the stomach, to which however no adhesions have been contracted. The 

 transverse duodenum passes behind the ascending colon, from which and from the colic portion 

 of the mesenterium commune it is free, the root of the mesentery persisting in its primitive 

 condition and not being extended by secondary adhesions caudad and to the right, in the direc- 

 tion of the iliac fossa. This is the explanation I believe of Hunter's : statement: "in this course 

 behind the mesentery it is exposed, as in most quadrupeds not being covered by it, as in the 

 human," which Weber finds difficult to understand. The ascending duodenum passes cephalad 

 and to the left, between the root of the mesentery and the descending colon, to both of which 

 it is adherent though to the colon only close to the duodeno-jejunal angle. This flexure is placed 

 immediately below the arch of the colon, the intestine here turning ventrad and to the right 

 at a sharp angle. Thus the loop of the duodenum with the included portion of the pancreas 

 and the root of the mesentery form a disk, to the front and left border of which the colon has 

 been applied, and which has contracted secondary adhesions dorsally to the parietes only along 



Hunter, John. Observations on the structure and economy of whales. Philos. Trans., 1787. 



