288 A Study of the Structural Unit of the Liver 
inserted into the cannule connected with the veins, with the following 
result : 
Blood rose in the tube in the 
Time Portal vein Hepatic vein 
1 minute. 5 cent. .0 cent. 
2 z ee (BH) 
3 ss Li eae SeDn ie 
4 ss ae w(O)5) 
5 oi IPR 5) Waly 
Further experiments show that at a given pressure it takes about as 
long for a liter of whipped blood to flow from the portal vein to the 
hepatic vein as in the opposite direction. Together these tests show that 
the artery communicates more freely with the portal vein than with the 
hepatic, apparently speaking in favor of Ferrein’s venous rootlets to the 
portal vein. If it is considered that under normal conditions there is a 
high blood-pressure in the portal vein, higher than in any other vein, it 
is not remarkable that an injection into the artery should flow more freely 
from the portal vein than from the hepatic vein. 
There seems to be no definite way to settle this question, except by 
making sections of injected specimens. If a cannula is tied into the 
hepatic vein and a single spurt of an aqueous solution of Prussian blue 
is made into it, it is found that numerous minute blue spots appear below 
the peritoneal surface of the liver. Sections of such specimens show that 
all of the fluid has entered the substance of the liver at the centers of 
portal units. If the injection is pushed a little farther—until the lobules 
are outlined—a large portion of the blue enters the terminal portal veins 
from the common capillary plexus of the lobule. As soon as this has 
taken place the fiuid backs into the larger veins, forms secondary injec- 
tions of other units and the picture becomes confused. In order to obviate 
this, I injected the artery with Prussian blue gelatin in which were sus- 
pended a large number of granules of cinnabar. The blue again flowed 
over into the portal and the hepatic veins, but the granules all lodged in 
the capillaries in the periphery of the lobule. Very few granules were 
found in any of the terminal portal twigs. This experiment shows at 
least that the bulk of the granules reach the capillaries of the lobule 
without passing through the portal vein. But an insignificant number 
of red granules are found lodged in the capillaries within the capsule of 
Glisson, and these encircle the bile ducts. 
The first experiment, with but a spurt of Prussian blue into the artery, 
shows that the long delicate arteries give rise to capillaries which form 
a plexus around the bile ducts and then enter the center of the portal 
