564 SPECIAL HISTOLOGY. 



the existence of the venous tissues or spaces of ancient and modern 

 anatomists, in the human spleen. The larger veins which still accom- 

 pany arteries, present no peculiarities, except in their width : all pos- 

 sess a memhrane, which is, at least upon the side of the artery, easy of 

 demonstration, and, like the vascular sheath, gradually becomes thinner. 

 Apertures of more minute veins, the so-called stigmata Malpighii, exist 

 only in inconsiderable numbers in the largest of these veins, while in 

 the smaller, they are more frequent. From the point of divarication of 

 the arteries and veins, the relations of the latter become somewhat dif- 

 ferent. In the first place, they give off upon all sides a vast number of 

 small veins, usually at right angles, whence their walls appear in places 

 almost cribriform ; and secondly, their membranes become completely 

 coalescent with the sheaths of the vesse]s, so that ultimately the two 

 constitute only a single very delicate wall, which, however, may still be 

 easily detected in the very smallest vessels that can be isolated by dis- 

 section. I find dilatations of any kind in no part of these veins, only, 

 it is to be observed that they become narrowed more slowly than the 

 arteries. Their continuity with the capillaries takes place in exactly 

 the same manner as in all other organs and may be demonstrated with- 

 out difficulty, by injecting the veins of a well-preserved human spleen, 

 especially of a child. Neither does any trace of dilatations present 

 itself in this case. 



The capillaries of the spleen have the ordinary structure, and a width 

 of 0'003-0'005 of a line; they are very numerous, and exist through- 

 out the pulp, where, round the Malpighian corpuscles, though not in 

 their coats, and elsewhere, they form a tolerably close network conti- 

 nuous through the whole spleen, only interrupted by the minutest trabe- 

 culse and by the Malpighian corpuscles. 



The human spleen possesses, relatively, very few lymphatics. The 

 superficial set are distributed sparingly between the two coats, but can 

 hardly be recognized, except in the neighborhood of the hilus and in 

 perfectly healthy spleens. The deep set may be discovered in the hilus, 

 whence also, few in number and small in diameter, they accompany the 

 arteries, but cannot be traced by any means so far as these. In the 

 hilus both sets of lymphatics join, traverse a few small glands, which 

 exist in this locality, and finally unite into a trunk which opens into the 

 thoracic duct opposite the llth or 12th dorsal vertebra. In diseased 

 spleens no trace of the superficial lymphatics can ordinarily be detected. 



The nerves of the spleen, consisting of many fine and a few thick 

 tubules, with a moderate proportion of Remak's fibres, are derived from 

 the splenic plexus, formed by two or three trunks which surround the 

 splenic artery, and are continued on the arteries into the interior of the 

 organ, each dividing into one or two branches, anastomosing here and 

 there. In the Sheep and Ox, these splenic nerves are truly colossal, so 



