Franklin P. Mall oy 
cism of the hterature upon the vascular system of the spleen, giving also 
a valuable experiment which throws light upon the circulation through 
the pulp. His conclusion regarding the arterial capillary is as follows: 
“ Die arterielle Capillare geht aus der Hiilsenarterie hervor und stellt 
ein diinnwandiges, leicht dehnbares Rohr dar von wechselnder Weite; 
ihre Wand besteht aus einer ausseren Schicht, welche aus stark in die 
Linge gezogenen Hiilsenzellen und anscheinend auch wirklich durch 
eine Fortsetzung der Hiilse selbst gebildet wird, und einer inneren 
Endothellage mit sparlichen, grossen Kernen. Diese Capillaren minden 
entweder unter spitzem Winkel direct in einen Milzsinus ein oder losen 
such durch Auffaserung ihrer Wand in dem Reticulum des Milzparen- 
chyms auf (p. 322).” Apparently Weidenreich has come to a con- 
clusion practically identical with that of W. Miller,’ although he made 
no direct injections (p. 340). 
Shortly after Weidenreich, Helly” published two papers upon the 
spleen with conclusions practically the same as mine and Thoma’s. He 
says: “Die Milz hat ein, iiberrall von einer regelmassigen Endothel- 
schichte ausgekleidetes, daher geschlossenes Gefisssystems mit sehr 
durchlassigen Wandungen” (Vol. 61, p. 272). Helly repeated Wei- 
denreich’s transfusion experiments and confirms him regarding the 
presence of foreign red blood corpuscles in the spleen pulp. According 
to Weidenreich these foreign cells passed over into the pulp from the 
capillary artery, and according to Helly they entered the pulp backward 
through the capillary vein. 
The quotations just given show that the recent authors are of one 
opinion regarding the large pores in the capillary walls. It appears that 
these openings are smallest according to Thoma, larger according to 
Helly, still larger according to Mall, and so large that they communicate 
most freely with the pulp-spaces according to Weidenreich. The prob- 
lem is further compheated by W. Miller, Weidenreich and others, who 
find that both open and closed capillaries occur in the same spleen. 
When we consider the difficulties and the differences of opinion, it is 
not hard to understand that there should be different conclusions re- 
garding this question. While I have found numerous direct capillary 
channels in the distended spleen, I have never seen one in the contracted 
spleen. Furthermore, I have never been able to follow anything lke 
an endothelial ning from an artery to a vein. So while the interpre- 
tations of the results are apparently different in the publications of 
*W. Miiller, Feinerer Bau der Milz, Leipzig, 1865, p. 79. 
>Helly, Arch. f. mik. Anat., LIX and LXI, 1902. 
