CH. xxiii.] THE SPLEEN. 323 



interior of the organ and, dividing and anastomosing in all parts, 

 form a supporting framework in the interstices of which the 

 proper substance of the spleen (spleen-pulp) is contained. 



At the hilus of the spleen, the blood-vessels, nerves, and lym- 

 phatics enter or leave, and the fibrous coat is prolonged into the 

 spleen substance in the form of investing sheaths for the arteries 

 and veins, which sheaths again are continuous with the trabeculse 

 before referred to. 



The spleen-pulp, which is of a dark red or reddish-brown colour, 

 is composed chiefly of cells, imbedded in a network formed of fibres, 

 and the branchings of large nucleated cells. The network so 

 formed is thus very like a coarse kind of retiform tissue. The 

 spaces of this network are only partially occupied by cells and 

 form a freely communicating system. Of 

 the cells some are granular corpuscles 

 resembling the lymph-corpuscles, both in 

 general appearance and in being able to 

 perform amoeboid movements ; others are 

 red blood-corpuscles of normal appearance 

 or variously changed ; while there are also 

 large cells containing either a pigment 

 allied to the colouring matter of the blood, 

 or rounded corpuscles like red corpuscles. 



The splenic artery, after entering the ^ 2?7 ._ Reticuluin of ^ 

 spleen by its concave surface, divides and spleen of a cat, shown by 



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subdivides, with but little anastomosis (Cadut.) 

 between its branches ; at the same time 



its branches are sheathed by the prolongations of the fibrous coat, 

 which they, so to speak, carry into the spleen with them. The 

 arteries soon leave the trabeculse, and their outer coat is then 

 replaced by one of lymphoid tissue ; they end in an open brush- 

 work of capillaries, the endothelial cells of which become con- 

 tinuous with those of the rete of the spleen-pulp. The veins 

 begin by a similar open set of capillaries from the large blood 

 spaces of the pulp. The veins soon pass into the trabeculoe, and 

 ultimately unite to form the splenic vein. This arrangement 

 readily allows lymphoid and other corpuscles to be swept into the 

 blood-current. 



On the face of a section of the spleen can be usually seen 

 readily with the naked eye, minute, scattered rounded or oval 

 whitish spots, mostly from ^ to ^ inch (-J- to | mm.) in diameter. 

 These are the Malpighian corpuscles of the spleen, and are 

 situated on the sheaths of the minute splenic arteries. They 

 are in fact outgrowths of the outer coat of lymphoid tissue 



Y 2 



