THE SPLEEN. 465 



The duct of the pancreas (fig. 150, d) (canal of Wirsung) extends the 

 entire length of the gland, and is somewhat nearer the lower than the 

 upper border. It begins in the tail of the pancreas, where it presents a 

 bifurcated extremity; and as it continues onwards to the head, it receives 

 many branches. It finally ends by opening into the duodenum, either in 

 union with, or separate from the common bile duct (p. 457). Of the tribu- 

 tary branches, the largest is derived from the head of the pancreas. 



The duct measures from T l ^th to j^th of an inch in diameter near the 

 duodenum. It is formed of a fibrous and a mucous coat : the latter is 

 lined by a cylindrical epithelium, and is provided with small glands in the 

 duct and its largest branches. 



Vessels, lymphatics, and nerves. The arteries and veins have been 

 described (p. 447); and the lymphatics join the lumbar glands. The 

 nerves are furnished by the solar plexus. 



THE SPLEEN. 



The spleen is a vascular spongy organ of a bluish or purple color, some- 

 times approaching to gray. Its texture is friable, and easily broken under 

 pressure. The use of the spleen is unknown. 



The viscus is somewhat elliptical in shape, and is placed vertically 

 against the great end of the stomach. Its size varies much. In the 

 adult it measures commonly about five inches in length, three or four 

 inches in breadth, and one inch to one inch and a half in thickness. Its 

 weight lies between four and ten ounces, and is rather less in the female 

 than the male. 



At the outer aspect it is convex towards the ribs, the inner surface is 

 marked by a longitudinal ridge, nearer the posterior than the anterior 

 border, into which the vessels plunge to ramify in the interior. Before 

 and behind the ridge, the surface is flattened or somewhat hollowed. The 

 spot where the vessels enter is named the hilum of the spleen. 



The anterior border is thinner than the posterior, and is often notched. 

 Of the two extremities, the lower is more pointed than the upper. 



Small masses or accessory spleens (splenculi), varying in size from a 

 bean to a moderate-sized plum, are found occasionally, near the fissure of 

 the spleen, in the gastro-splenic omentum, or in the great omentum. 



STRUCTURE. Enveloping the spleen are two coverings, a serous and a 

 fibrous. It is formed by a network of fibrous or trabecular tissue, which 

 contains in its meshes the splenic pulp, with the Malpighian corpuscles. 

 Throughout the mass the bloodvessels and the nerves ramify. No duct 

 exists in connection with this organ. 



The serous or peritoneal coat incases the spleen, and covers the surface 

 except at the hilum and the posterior border. It is closely connected to 

 the subjacent fibrous coat. 



T^he fibrous coat (tunica propria) gives strength to the spleen, and forms 

 a complete case for it. At the fissure on the inner surface this investment 

 passes into the interior with the vessels, to which it furnishes sheaths : 

 and if an attempt is made to detach this coat, numerous fibrous processes 

 will be seen to be connected with its inner surface. Its color is whitish ; 

 and its structure is made up of areolar and elastic tissues. 



Dissection. The spongy or trabecular structure will best appear, by 

 washing and squeezing a piece of fresh bullock's spleen under water, so as 

 to remove the grumous-looking material. 

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