The method of termination of the pancre atic duct, and its relation to the ductus cho ledochus, is rather curious. The duct, unlike the ducts of the salivary glands, which have a long course after leaving the gland before they terminate, passes at once from the gland to tbe intestine at a point where the former is closely applied to the latter, so that it is quite covered up and has no peritoneal in vestnaent. At this situation it comes into contact, at an acute angle, with the ductus choledochus, which has descended to this point either in a groove of the pancreas, between it and the intestine, or in a complete channel through the gland substance. The pancreatic is placed to the left of the choledoch duct ; and, maintaining this relation, the two perforate obliquely the duodenum about the middle of its second portion and at the left side of its posterior wall.
Side by side they perforate in succession the muscular, the fibrous, and the mucous coats, which they elevate into a ridge when injected or when a probe is passed into them, and after an oblique course of about eight lines, they open into the bottom of a little papilla situated in a transverse fold near the junction of the middle with the third portion of the duodenum.f In their transit through the walls of the intestine they are separated by a valve-like process, composed of the tissues that constitute their walls, which gradually gets thinner and thinner till it terminates at the base of the little olive-shaped ampulla about two lines in depth, into which the cavity of the papilla is dilated ; and since the mucous membrane lining this ampulla is of the same structure as that lining the intestine, and unlike that lining the ducts, these latter must be said to open by two distinct orifices at the base of the papilla, and not by one at its apex, as is usually described ; in fact the lining membrane of the cavity of the papilla is part of the general mucous surface of the duodenum.* Towards its orifice the duct more or less enlarges itself ; but at its very aperture, on the contrary, it undergoes a contraction. The appearance of a valve guarding the orifice depends merely on the partition which separates its mouth from that of the choledoch duct. Occasionally near the orifice, occasionally higher up, there is a valve-like process projecting from its inner surface ; but this is not constant either in its situation or its existence.
Froin the narrowness of the duodenal ori fice of the pancreatic duct, from the movable and yielding nature of the eminence upon which it opens, and from the oblique course of the duct through the walls of the duo denum, it follows that the pancreatic fluid and the bile may pass freely into the duode MIM, but cannot regurgitate from it into the ducts. " On this subject," says Cruveilhiert,
" I have made several experiments. I have forcibly injected both water and air into the duodenum, included between two ligatures, but nothing escaped; on the other hand, I have injected the same fluids from the duct into the duodenum, which I was thus able to distend at pleasure. But then, on com pressing the bowel with great force, I have never been able to cause the slightest re flux into the ducts." The spur-like process formed by the lining membrane reflected upon itself at the junction of the ductus choledochus and the pancreatic duct, ex tending down to the duodenal orifice, does not prevent the fluid of one canal from passing into the other. Thus the pancreatic fluid might regurgitate into the ductus choledochus, and, on the other hand, the bile might enter the pancreatic duct, if these canals were not habitually full. Moreover, this spur-shaped process between the two canals cannot arrest the flow either of the bile or pancreatic fluid, by being applied to the orifice of the one or the other duct.
Fig. 56. is a diagrammatic representation of the manner in which the ducts traverse the walls of the duodenum and terminate_in the papilla, and of their relation to one another, and to the coats of the intestine.
Vessels. —The arteries of the pancreas, which, for the size of the gland, are large and numerous, are, like those of other conglomerate glands, contributed from many sources, and are derived from the branches of the cceliac axis, and from the superior mesenteric. The principal are the pancreatico-duodenalis of the hepatic and the pancreatic branches of the spicule artery,—one of which, the pancrea Ilea magnet, sometimes runs nearly the whole length of the gland, accompanying the duct from left to right. The branches froro the superior mesenteric are mostly derived from that small twig which, given off just at the lower border of the pancreas, anastomoses with the pancreatico-duodenalis. The veins empty themselves into the superior mesenteric and splenic.
The lymphatic vessels have not, that I know of, been demonstrated, nor have I been able to detect them myself: they are supposed to enter the lumbar glands in the neighbourhood.
The nerves are derived from the solar plexus, and enter the gland at different parts, accom panying the branches from the arteries of the cceliac axis.