156 SPECIAL HISTOLOGY. 



upon the arteries which support the splenic corpuscles. As 

 to their terminations, I can only state that they pass into the 

 pulp, and are still to be met with upon the arterial penicilli. 

 Here they ultimately become as delicate as the finest capillaries, 

 no longer possess dark edged tubules, and, according to Ecker's 

 observations (1. c, p. 149, fig. 10), probably end in free dichoto- 

 mous divisions. In the Calf, the nerves upon arteries of 1"' 

 measure 0024 — 0*028'", on the penicilli arteriarum 0*0048 — 

 00056"', in the midst of the pulp 0*003 — 0*004'". In branches 

 of 012 — 0*028'", I here still found a single dark edged nerve- 

 tubule, whilst all the rest consisted of a striated nucleated 

 tissue, which alone constituted the finer threads. It is impro- 

 bable that this structure has here, as in the trunks, the import 

 of Remak's fibres ; I should rather, with Ecker, consider it 

 to be embryonic nervous tissue, such as we are sufficiently 

 acquainted with in other localities ; and I am inclined to 

 believe that the dark edged tubules of the trunks finally pass 

 into pale fibres, as such compose entirely or almost entirely the 

 ultimate twigs, and then terminate by branching out. In the 

 trunks of the splenic nerves of the Calf, there are found, before 

 their entrance into the spleen and within it, numerous dichoto- 

 mous divisions of the dark edged, partly coarser and partly finer 

 primitive tubules, such as I have not hitherto succeeded in 

 detecting in Man. 



[In regard to the structure of the veins, many of the 

 Mammalia appear to resemble Man, while others, as the Horse, 

 Ox, Sheep, Pig, present very wide differences. In these ani- 

 mals a special venous membrane and a vascular sheath are found 

 only at the origins of the largest venous trunks, while further in, 

 they are visible only upon the side of the arteries. In all the 

 smaller veins, which run independently (without arteries), no 

 further trace of two coats is to be met with, in fact, these veins 

 appear to be mere excavations in the substance of the spleen, 

 especially as a number of anastomosing trabecules with red 

 pulp often forming projecting knobs between them, are appa- 

 rent upon their walls. However, they always have a perfectly 

 smooth and shining surface, arising from spindle-shaped, tes- 

 selated epithelium- cells of 0*005 — 0*01'", which are only mi- 

 croscopically demonstrable. This epithelium corresponds per- 



