OBSERVATIONS ON THE STRUCTURE OF THE SPLEEN, 367 
days more this is exchanged by 3 per cent., and finally the 
bits of spleen are placed in alcohol and used for sections, 
which are prepared in the usual way. 
To begin the hardening with a stronger solution of chromic 
acid than 1 per cent. is, according to my experience, objec- 
tionable, as stronger solutions tend to damage the material ; 
for the same reason I do not think it advisable to increase 
the strength of the acid too soon. 
I ought not to omit to add that injecting the spleen of 
the dog, as well as that of man, with Miiller’s fluid instead 
of osmic acid, after the injection with saline solution, is 
also a very good plan. Hematoxylin I found indispensable 
in my Investigations. —, 
Asis very well known (Kolliker, 1. c., pp. 449 and 450) the 
capsule as well as the trabecule of the spleen contain un- 
striped muscular tissue, the amount of which varies in 
different animals. With regard to man Kyber (1. c., p. 546) 
confirms the assertions of W. Miller, according to whow 
slender bundles of unstriped muscles exist in the capsule as 
well as in the trabeculee. Meissner had also seen them in the 
spleen of man; Frey mentions them only in the trabecule, and 
several other authors, as Gerlach, Gray, Stinstra, Henle and 
Kolliker could not find any in the spleen of man. 
This is what I find: in the dog the capsule contains in 
that half which is next the parenchyma a continuous mass of 
unstriped muscles, whose bundles are arranged parallel to 
the longitudinal axis of the whole organ ; above this longi- 
tudinal coat there are small circular (é.e., running in a direc- 
tion parallel to the short axis of the organ) muscle-bundles 
embedded in a matrix composed of connective-tissue and 
elastic tissue, which latter forms, nearest to the surface, 
regular elastic lamin. Near the somewhat sharp edges of 
the organ circular bundles are present also inside the longi- 
tudinal muscular coat. The trabecule are almost completely 
composed of muscles. In the spleen of monkeys the capsule 
contains a thin layer of longitudinal muscles in the deeper 
part only, whereas the trabecule possess a great amount of 
muscular tissue ; at those places where the trabeculze join the 
capsule, they (the trabecule) are all through made up of un- 
striped muscles. In the human spleen the capsule contains 
sparingly muscular bundles, and generally at those points 
only where the trabecule are inserted into the capsule. The 
larger trabeculae, including the larger branches of the splenic 
artery and vein, contain in their periphery numerous bundles 
of unstriped muscles; the smaller trabecule also contain 
muscular bundles. I am surprised to find so many small 
VOL, XV.—NEW SER. BB 
