734 SPECIAL PHYSIOLOGY, 



The proper coat, the sheaths of the vessels, and the trabeculae, con- 

 sist of white fibrous and areolar tissues, mixed with elastic fibres, and 

 contain, especially in animals, pale, fusiform, unstriped muscular fibre- 

 cells. The splenic pulp consists of a colorless, granular parenchyma, 

 mixed with numerous colored cells, with red blood-corpuscles of vari- 

 ous size, shape, and state of aggregation. The colorless parenchyma 

 is composed of round, oval, and fusiform nucleated cells, of nuclei, 

 and of a granular matrix : it somewhat resembles the contents of the 

 sacs of the solitary and agminated intestinal glands. The colored 

 cells, or altered red blood-corpuscles of the splenic pulp, are peculiar 

 to this organ. Some closely resemble the ordinary red blood-corpus- 

 cles ; others, however, are smaller, 'and of a bright golden color, 

 brown, or black ; sometimes their contained pigment is gathered into 

 a rod-shaped mass, or into some crystalline form, or is broken up into 

 minute granules. Frequently they present the unique condition of 

 agglomeration into little clusters or heaps, which are sometimes free, 

 but sometimes inclosed in a delicate membrane, or encysted, so as to 

 appear like large compound cells, containing from two or three, to as 

 many as twenty altered blood-corpuscles. 



Embedded in the splenic pulp, are numerous whitish vesicular bod- 

 ies, measuring from Jth to Jd of a line in width, named the Malpig- 

 hian corpuscles of the spleen ; they are attached, in clusters, to the 

 small arteries, and are supported on the trabeculae. so as to appear 

 like sessile buds or fruit upon a stem. Their envelope is partly de- 

 rived from the fibrous coat of the artery, and partly from the outer 

 harder layers of their contents. Their cavities have no communication 

 with the bloodvessels on which they rest. Smaller bodies found in 

 the spleen, are said to be Malpighian corpuscles in an immature state. 

 They are composed of an extremely delicate, imperfectly fibrous, en- 

 velope, inclosing granular, nuclear, and nucleated-cell elements, like 

 those of the splenic pulp itself. 



The splenic arteries, entering at the hilus, ramify through the spleen 

 by rapid subdivisions, without anastomoses, after the manner of the 

 branches of a tree; many quickly divide into a coarse capillary net- 

 work, which as speedily ends in the minute veins. The capillaries are 

 most abundant in the splenic pulp, and also on the surface, and in 

 the interior, of the Malpighian corpuscles. The smallest veins chiefly 

 end, almost immediately, in larger ones, which form close plexuses 

 and venous diverticula between the trabeculae. Recent researches 

 show, that whilst some of the arteries end in capillaries, from which 

 veins arise in the usual manner, other of these vessels end in veins 

 which suddenly enlarge, and, lastly, others even terminate in lacunce, 

 or spaces destitute of distinct walls, but bounded only by the elements 

 of the pulp. (Gray, Billroth.) The interior of some of the veins pre- 

 sents a closely dotted appearance, from the numerous openings of 

 little venules or diverticula around them. In the blood of the veins, 

 splenic cells, altered blood-corpuscles, and clustered blood-corpuscles, 

 are sometimes found, as from mutual extra- and intra-vasation. The 

 blood of the splenic veins contains, however, fewer red corpuscles, but 

 more fibrin, than other venous blood. On escaping from the hilus, 



