750 ORGANS OF DIGESTION. 



The body of the pancreas is convex in front, and covered by the ascending 

 layer of the transverse meso-colon and the posterior surface of the stomach. 



The posterior surface is concave, and has the following structures interposed 

 between it and the first lumbar vertebra : the superior mesenteric artery and 

 vein, the commencement of the vena portae, the vena cava, the aorta, the left 

 kidney, the suprarenal capsule, and the corresponding renal vessels. 



The upper border is thick, and has resting upon it, near its centre, the coeliac 

 axis ; the splenic artery and vein are lodged in a deep groove or canal in this 

 border ; and to the right, the first part of the duodenum and the hepatic artery 

 are in relation with it. 



The lower border, thinner than the upper, is separated from the transverse 

 portion of the duodenum by the superior mesenteric artery and vein ; to the left 

 of these the inferior mesenteric vein ascends behind the pancreas to join the 

 splenic vein. 



The pancreatic duct, called the canal of Wirsung from its discoverer, extends 

 transversely from right to left through the substance of the pancreas, nearer to 

 its lower than .its upper border, and lying nearer its anterior than its posterior 

 surface. In order to expose it, the superficial portion of the gland must be re- 

 moved. Traced backwards, it is found to commence by an orifice common to 

 it and the ductus communis choledochus, upon the summit of an elevated 

 papilla, situated at the inner side of the descending portion of the duodenum, a 

 little below its middle ; from this papilla it passes very obliquely through the 

 mucous and muscular coats, separates itself from the ductus communis chole- 

 dochus, and, ascending slightly, runs from right to left through the middle of 

 the gland, giving off numerous branches, which commence in its lobules. 



Sometimes the pancreatic duct and ductus communis choledochus open sepa- 

 rately into the duodenum. The excretory duct of the lesser pancreas is called 

 the ductus pancreaticus minor ; it opens into the main duct near the duodenum, 

 and sometimes separately into that intestine, at a distance of an inch or more 

 from the termination of the principal duct. 



The pancreatic duct, near the duodenum, is about the size of an ordinary 

 quill ; its walls are thin, consisting of two coats, an external fibrous and an 

 internal mucous ; the latter is thin, smooth, .and furnished, near its termination, 

 with a few scattered follicles. 



Sometimes the pancreatic duct is double, up to its point of entrance into the 

 duodenum. 



In structure, the pancreas closely resembles the salivary glands ; but it is 

 looser and softer in its texture. The fluid secreted by it is almost identical 

 with saliva. 



Vessels and Nerves. The arteries of the pancreas are derived from the splenic, 

 the pancreatico-duodenal branch of the hepatic, and the superior mesenteric. 

 Its veins open into the splenic and superior mesenteric veins. Its lymphatics 

 terminate in the lumbar glands. Its nerves are filaments from the splenic* 

 plexus. 



THE SPLEEN. 



The Spleen is usually classified, together with the thyroid, thymus. and supra- 

 renal capsules, as one of the ductless, or blood-glands. It possesses no excre- 

 tory duct. It is of an oblong flattened form, soft, of very brittle consistence, 

 highly vascular, of a dark bluish-red color, and situated in the left hypochon- 

 driac region, embracing the cardiac end of the stomach. It is invested by 

 peritoneum, and connected with the stomach by the gastro-splenic omentum. 



Relations. The external surf ace is convex, smooth, and in relations with the 

 under surface of the Diaphragm, which separates it from the ninth, tenth, and 

 eleventh ribs of the left side. The internal surface is slightly concave, and 

 divided by a vertical fissure, the hilum, into an anterior or larger, and a posterior 

 or smaller portion. The hilum is pierced by several large irregular apertures, 



