CHAPTER XXV. 



THE SPLEEN, PANCEEAS, THYMUS, THYBOID AND PINEAL 

 GLANDS, AND PITUITARY BODY. 



Br C. L. DANA, A.M., M.D., 



Professor of Physiology in the Woman's Medical College, New York City. 



General structure. This organ is composed of connective 

 tissue and muscular fibres, containing Malpighian corpuscles, 

 pulp-substance, blood-vessels, lymphatics, and nerves. An 

 outline of the general arrangement of these several elements 

 will make subsequent details clearer. 



Within its peritoneal investment the spleen has, in the 

 first place, an elastic fibrous capsule ; this envelops the organ 

 and passes into its interior at the hilum. From the internal 

 surface of the capsule are given off fibrous bands and pro- 

 cesses the trabeculse, which interlace and form a fine network. 

 In the meshes of this network is a soft, reddish substance the 

 splenic pulp. The arteries, entering at the hilum, run along 

 the trabeculse and end in capillaries, which gradually break up 

 in the parenchyma. Attached to the walls of the arterioles 

 and bathed in the spleen-pulp are little bodies, called the 

 Malpighian corpuscles. The veins begin in the pulp, and, 

 gradually enlarging, pass out alongside the arteries. The 

 blood thus passes out of the capillaries, into the spleen -pulp, 

 and from thence is collected by the veins. It passes through 

 the blood-paths in the pulp much as the lymph passes through 

 lymph-paths in the lymphatic glands. 



This unique structure is now to be considered in detail. 



The peritoneal or serous coat of the spleen resembles the 

 peritoneum elsewhere. It is, in man especially, very firmly 



