684 ORGANS OF DIGESTION. 



duodenum. The excretory duct of the lesser pancreas is called the ductus pan- 

 creaticus 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. 



The Structure of the pancreas closely resembles that of 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. The nerves are filaments from the splenic 

 plexus. 



THE SPLEEN. 



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

 thymus glands, as one of the ductless glands, from its possessing no excretory 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 hypochondriac region, em- 

 bracing the cardiac end of the stomach. It is invested by peritoneum, and 

 connected with the stomach by the gastro-splenic omentum. 



Relations. Its external surface is convex, smooth, and in relation 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 

 hilus, into an anterior or larger, and a posterior or smaller portion. The hilus is 

 pierced by several large, irregular apertures, for the entrance and exit of vessels 

 and nerves. At the margins of the hilus, the two layers of peritoneum are 

 reflected from the surface of the spleen on to the cardiac end of the stomach, 

 forming the gastro-splenic omentum, which contains between its layers the splenic 

 vessels and nerves, and the vasa brevia. The internal surface is in relation, in 

 front, with the great end of the stomach ; below, with the tail of the pancreas ; 

 and behind, with the left crus of the Diaphragm and corresponding supra-renal 

 capsule. 



Its upper end, thick and rounded, is in relation with the Diaphragm, to which 

 it is connected by a fold of peritoneum, the suspensory ligament. 



Its lower end is pointed ; it is in relation with the left extremity of the trans- 

 verse arch of the colon. 



Its anterior margin is free, rounded, and often notched, especially below. 



Its posterior margin is rounded, and lies in relation with the left kidney, to 

 which it is connected by loose areolar tissue. 



The spleen is held in its position by two folds of peritoneum ; one, the gastro- 

 splenic omentum, connects it with the stomach, and the other, the sus2)ensory 

 ligament, with the under surface of the Diaphragm. 



The size and weight of the spleen are liable to very extreme variations at 

 different periods of life, in different individuals, and in the same individual under 

 different conditions. In the adult, in whom it attains its greatest size, it is usually 

 about five inches in length, three or four inches in breadth, and an inch or an inch 

 and a half in thickness, and weighs about seven ounces. At birth, its weight, in 

 proportion to the entire body, is almost equal to what is observed in the adult, 

 being as 1 to 350 ; whilst in the adult it varies from 1 to 320 to 1 to 400. In old 

 age, the organ not only decreases in weight, but decreases considerably in pro- 



