CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 773 



cells, the branches of which are membranous and flange-like rather 

 than filamentous. These flanges of neighbouring cells join with 

 each other, and thus form a labyrinthine network, the walls of the 

 minute passages of which are formed not of fibres but of irregular 

 sheets. In some parts of the spleen, however, these flange-like 

 processes are replaced by fibres, and, the bodies and nuclei of the 

 constituent cells being rare, the reticulum appears as a more 

 ordinary reticulum of fine fibres. 



The bars of this reticulum, whether flange-like or filamentous, 

 are at the edges of the trabeculse continuous with the substance of 

 the trabeculse ; the smaller trabeculae break up into the reticulum, 

 and the larger trabeculse are fringed with processes continuous 

 with the bars of the reticulum. Thus the coarser network of the 

 trabecular system is continuous with the finer network of the 

 reticulum. 



The reticulum of the lymphatic gland contained, it will be 

 remembered, besides fluid, leucocytes, these being crowded in 

 the follicle and more sparse in the lymph-sinus. The splenic 

 reticulum also contains leucocytes and other cells, but these are 

 thrown into the background by the large number of red corpuscles 

 with which the meshes of the reticulum are crowded. The reti- 

 culum in fact is filled with blood ; and peculiar arrangements exist 

 by which the blood gains access to the spaces of the reticulum. 

 What we spoke of above as ' spleen pulp ' expressed from the fresh 

 spleen consists of fragments of the reticulum together with the red 

 and white corpuscles and other cells occupying the meshes of that 

 reticulum. 



471. The splenic arteries entering the spleen at the hilus 

 are in some animals at first supported by the trabeculse, along 

 which they run dividing as they go, but the branches at last leave 

 the trabeculse and plunge into the reticulum. In other animals 

 the arteries run more independent of the trabeculae. As they 

 leave the trabeculse, or towards their terminations, the small 

 arteries are apt to divide into pencils of small twigs. In a similar 

 manner the veins may be traced back along the trabeculse, small 

 and great, along which they are gathered up from smaller veins of 

 the reticulum; but the veins do not run in the reticulum as distinct 

 vessels to the same extent that the arteries do. 



In the reticulum the minute arteries, according to most 

 observers, are not continuous in the usual manner with veins by 

 means of closed capillaries ; but a peculiar arrangement is met 

 with. The epithelioid plates forming the capillary wall, instead 

 of being cemented together to form a continuous tubular sheath, 

 are separate from each other, come asunder as it were, and thus 

 allow the lumen of the capillary or rather of the minute artery to 

 open out into the splenic reticulum ; indeed the epithelioid plates 

 no longer retain their simple spindle shape, but becoming branched 

 and irregular are transformed into the cells of the reticulum. 



