358 THE SPLEEN, BY WILHELM MULLER. 



Schweigger-Seidel. After a longer or shorter course the capil- 

 lary wall becomes much attenuated and finely granular, the 

 nuclei surrounded with a distinct mass of protoplasm, their 

 continuity interrupted, and finally the homogeneous wall 

 breaks up into small strise, to which the cells are attached, and 

 which are continuous with the cellular and fibrous plexus of 

 the pulp. Through the spaces thus produced in the primary 

 capillary wall the blood escapes into the cavities formed by 

 the cellular and fibrous plexuses of the pulp, that is to say, 

 into the intermediate blood passages. From the latter the 

 blood is collected into the rootlets of the veins. These com- 

 mence as cribriform, interrupted canals, the boundaries of 

 which are essentially formed of lymph corpuscle-like cells and 

 a delicate intercellular substance, constituting a plexus with 

 numerous lacunae. After a short or, as in man and rabbits, 

 a somewhat longer course, the vein obtains a continuous in- 

 ternal investment, consisting of a layer of fusiform epithelial 

 cells with spheroidal nuclei, which not unfrequently project 

 into the lumen of the vessel, the superjacent connective tissue 

 layer becoming at the same time condensed, causing the lymph 

 corpuscle-like cells to crowd more closely together, and the 

 fibrillar intercellular substance to become more distinct, whilst 

 it pursues a transverse direction, and forms a tolerably close 

 plexus (Henle). The smaller venous branches unite like the 

 branches of trees to form larger trunks, investing which a 

 tunica adventitia, consisting of longitudinal connective tissue 

 fibrils with interspersed cellular elements, soon makes its ap- 

 pearance. The cylindrical muscular fasciculi belonging to the 

 adjoining trabeculse attach themselves longitudinally to these 

 branches, and immediately become firmly adherent to their 

 walls. As this occurs every now and then at different points, 

 the gradually enlarging venous ramuscules obtain their already 

 described compact walls, resembling those of the sinuses of the 

 dura mater, and which they retain up to their point of exit 

 from the organ. 



The foregoing description of the arrangements of the circulating 

 apparatus in the spleen rests (1) on the observation that, in recently 

 hardened spleens still containing blood, both in the embryo (Pere- 

 meschko) and in the adult (W. Miiller), the tissue of the pulp is con- 



