$70 DR. £. KLEIN. 
pulp of young rats and half-grown dogs; they are less 
numerous in young dogs, and in man only rudiments of them 
can be found. 
The examination of the pulp of the human spleen proved 
extremely successful with regard to the stroma, especially in 
the case of the enlarged spleen at the early stage of enteric 
fever, for here the latter is found to consist of beautiful flat- 
tened nucleated cells which form the elements of the honey- 
comb of membranes. (Compare figs. 2 and 3.) Into the 
smaller spaces of the honeycomb a nucleated knob is occasion- 
ally seen to project, being distinctly an outgrowth of the 
general matrix. From what has been said with respect to 
the dog’s spleen it is only fair to conclude that also here 
these nucleated knobs represent the early stage in the de- 
velopment of the so-called lymphoid pulp- -cells. ‘The flat- 
tened cells of the matrix become at certain places so arranged 
as to forma continuous row of cells which, projecting on one 
surface freely into the cavity of a venous sinus, represent the 
endothelial wall of this latter. In fig. 4, which illustrates 
this point very well, a and B represent the wall of a venous 
sinus seen lengthways ; the surface a is directed into the 
lumen of the vein. Also into these venous cavities nucleated 
knobs are found to project, and besides, some of the cells 
forming the wall of the sinus contain a constricted nucleus 
or even two nuclei; thus showing that there is a good deal 
of foundation for the assumption previously mentioned, viz., 
that nucleated knobs bud from the cellular stroma of the 
pulp, and become finally detached so as to form lymphoid 
corpuscles, which being carried away by the blood current 
represent colourless blood corpuscles. In very many cases 
the flattened cells of the stroma present a very peculiar ap- 
pearance in the profile-view ; this consists in one of their 
surfaces showing numerous small notches more or less regu- 
larly distributed. (Compare figs. 3 and 4.) I am not able 
to determine with certainty the meaning of this appearance ; 
but it seems to me to be probably due to one surface of the cells 
being provided with linear thickenings. A similar appearance, 
but much more marked and in accordance with the explanation 
just given, 1s found in the wall of the venous sinuses of the 
splenic pulp of monkeys. In fig. 6 these venous sinuses 
(injected) are seen in transverse sections, their cellular wall 
seems to possess small rodlike structures which are evidently 
due to linear thickenings—as it were to ridges—running 
parallel to the longitudinal axis of the vein. 
Thus it is seen that in the human spleen as well as 
in that of the dog the structure of the stroma of the pulp 
