The Ampulla of Vater. 177 



the folds. The duct of Santorini in its passage through the 

 wall of the intestine is also well guarded by valvular folds with 

 their free edges toward the orifice, and is therefore well calcu- 

 lated to prevent any regurgitation of liquid or the entrance of 

 solid substances. In this duct, the folds are seen to increase in 

 number toward the orifice, as is the case with the ductus chol- 

 edochus and the duct of Wirsung (PI. XIV., Fig. i, and PI. 

 XIII., Figs. I and 2). 



The duct of Santorini seems to be kind of a reserve, and it 

 may be the main channel for carrying the pancreatic juice, as 

 is shown by its occasional great size in the cat and in man 

 (1,389), while in the dog it is normally the larger (1,386; 22,510). 

 Doubtless, in any case if the duct of Wirsung becomes clogged, 

 it would assume the entire office of both ducts. In the foetal 

 dog and cat two ducts are of very nearly the same size and 

 appear to be potentially of equal importance.* 



In conclusion, it seems to me that the weight of evidence is 

 greatly in favor of considering the ampulla of Vater as an ap- 

 pendage of the ductus choledochus or of the duct of Wirsung, 

 and not of the duodenal mucous membrane. And, as the am- 

 pulla has been found so constantly whenever the two ducts 

 enter the intestinal wall separately, and open by a common 

 orifice, I would suggest that Duvernoy be followed in his 

 opinion, viz., that the ampulla belongs to both ducts. 



Summary. 



1. The pancreas in the cat is constantly provided with two 

 anastomosing ducts of unequal size which open separately 

 into the intestine. 



2. One of the ducts, usually the larger, after passing through 

 the muscular coat of the duodenum, opens into its lumen 

 through a contracted orifice common to it and the ductus 

 choledochus. 



3. The ducts have been named, from their size, principal and 

 accessory; but the comparative size is variable; and as position 

 in morphology is doubtless of much greater importance than 

 size, names should be used which have no reference to size. 

 Accordingly, in this paper, the following names, sanctioned by 

 high authority, have beer, used: — Duct of Wirsung, for the 



*It would be of the greatest interest to know whether the Dancreatic ducts are developed simuha- 

 neously, or one earlier than the other, as is the case in the chick (11,133). 



