MINOT : SINUSOIDAL CIRCULATION. 
197 
spaces grow and at the same time the mesenchymal tissue between 
the tubules gradually disappears, and the endothelium fits itself 
against the tubules, and thus the blood spaces appear as true 
sinusoids. There are of course capillaries in the glomeruli. 
I have examined carefully many embryos of dog-fish, chicks, rab¬ 
bits and pigs, and have seen no indication of the development of 
true capillaries in the Wolffian body between the tubules. From 
their first appearance the blood channels are larger than capillaries 
and are in direct or almost direct communication with the vein. 
We must then regard these sinusoids as morphologically expansions 
of, or modifications of a venous blood channel. Our present knowl¬ 
edge of the development of the Wolffian sinusoids is very incom¬ 
plete, but in my judgment it sufficiently justifies the conclusion 
reached. Moreover in the case of the liver the transformation of the 
venous channel into complicated sinusoids can be demonstrated 
with ease and certainty^ 
As regards the adult Wolffian body, it is probable that the sinu¬ 
soidal type of circulation is obliterated, at least in the organ of 
Rosenmuller and Girald&s. Czermy, ’89.1, figures only small blood 
vessels not fitting against the tubules of Girald&s. D. Popoff, ’93.1, 
p. 300 and Fig. 11, found the tubules of the human parovarium 
towards the end of pregnancy, at birth, and after birth, to have lost 
the sinusoids. Instead of a blood space, he found around each 
tubule an inner thicker coat of longitudinally elongated cells and a 
thinner outer coat of concentrically elongated cells; both coats are 
apparently mesenchymal. 
Conclusion : The intertubular blood circulation of the embry¬ 
onic mesonephros is sinusoidal in elasmobranchs , amphibians , 
birds and mammals. After the tubules in the embryo hare become 
coiled , there occurs an intercrescence of the endothelium of the car- 
dined vein and of the tubules , which finally results in the formation 
of sinusoids. 
3. Liver. The intimate relations of the hepatic cylinders to the 
veins in the developing liver are, of course, familiarly known to all 
embryologists, and have become matters of text-book description; 
see for example Prenant, ’96.1, Livre 2, p. 290; O. Ilertwig, ’96.1, 
p. 318 ; J. Kollmann, ’98.2, p. 368 ; or (). Schultze, '97.3, p. 381. The 
description of the last is particularly concise and clear, and may 
therefore be quoted. “ Gleichzeitig [i. e. am elften Tage] mit der 
Bildung des rechten Leberganges erscheinen beim Kaninchen auch 
