384 PRACTICAL ANATOMY. 



it presents a longitudinal fissure the hilum ; its anterior 

 border presents a notch. The spleen is invested by a 

 fibrous coat, which contains involuntary muscular fibres 

 and much yellow elastic tissue in its structure. It is 

 reflected into the organ at the hilum, forming the large 

 splenic canals. Its under surface sends off trabeculse, 

 which constitute the skeleton of the spleen. In truth, 

 the spleen may be said to consist of a sponge-work of 

 fibrous trabeculse, derived from the fibrous coat. The 

 meshes of the trabeculae hold the splenic pulp. This 

 consists of a dark-red substance, consisting of interlacing 

 connective-tissue cells, forming a skeletal arrangement to 

 support the pulp, which consist of blood-corpuscles in 

 all stages of development and decay and free haemoglobin. 

 The splenic artery breaks up into minute capillaries, the 

 walls of which consist of proliferating lymphoid elements. 

 The capillaries open directly into the meshes of the 

 spleen. The Malpighian corpuscles of the spleen are 

 collections of lymphoid elements along the course of the 

 arterioles ; they are nodular masses, about one-fiftieth 

 inch in diameter. The changes effected in the blood in 

 the spleen are briefly the genesis of white corpuscles out 

 of the lymphoid tissue ; possibly, the genesis of the red 

 corpuscle, and certainly the destruction of effete cor- 

 puscular elements and the liberation of the haemoglobin. 



THE KIDNEYS. 



The kidneys, two in number, are placed against the 

 posterior wall of the abdomen behind the peritoneum. 

 They extend from the twelfth rib to the crest of the 

 ilium, the right being a trifle lower than the left. They 

 are about four inches long, two broad, and one thick ; 

 weigh about five ounces, a little less in the female ; of 

 a dark-red color, friable being readily torn and com- 



