THE SPLEEN. 157 



fectly with that of the larger veins, only that here it no longer lies 

 upon a special wall, but immediately upon the substance of the 

 spleen, i. e. upon the trabecules and upon a delicate membranous 

 substance which bounds the pulp between them. Under these 

 circumstances we may, with perfect justice, speak of venous 

 sinuses ; the more, if we consider that these, so to say, wall-less 

 veins have a colossal width, and are pierced by innumerable 

 veins which open into them. These smaller veins, again, may 

 be traced for a considerable distance with the scissors, but I 

 have as yet never been able to succeed in demonstrating in 

 what manner they are continuous with the capillary network, 

 proceeding from the penicilli arteriarum, which here also is very 

 distinct. I can hardly believe that it will ever be possible to 

 make out this continuity completely, for the finest veins, which 

 are often bounded by but a few trabecule, and indeed for the 

 most part by the red pulp alone, are such delicate canals, that 

 the slightest mechanical force, as in inflating or injecting 

 them, destroys them ; and even by the microscope they are not 

 discoverable. It may always be observed, however, that they 

 eventually become very minute, so small that it is impossible 

 to consider their origins as enlargements. For my own part, I 

 believe, that here also, the connection with the capillaries takes 

 place quite in the ordinary manner, with this distinction, how- 

 ever, that the veins in arising from them possess only one 

 membrane, an epithelium, and are therefore perhaps connected 

 in some other manner with their structureless coat. Smaller 

 series of more rounded epithelial cells, which are not unfre- 

 quently found on teasing out the pulp, probably belong to the 

 smallest veins. 



In mammalia the lymphatics are stated by all authors to be 

 extremely numerous, and this is perfectly true for the superficial 

 vessels, which in the Calf, for example, are exceedingly abundant 

 and present numerous anastomoses in the subserous cellular 

 tissue. On the other hand, I find that the deeper lymphatics 

 are scanty. In the hilus of a calf s spleen, for instance, I found 

 but four lymphatic trunks with a collective diameter of 0*1 7'". 

 The superficial and deep lymphatics would appear to be, to a 

 certain extent, connected ; inasmuch as a few scattered 

 lymphatics, which are probably connected with those which 

 proceed from the hilus, accompany the arteries which pass 



