ras) 
~2 
2 A Study of the Structural Unit of the Liver 
capillaries arise from the hepatic vein it is encircled by the red mass. It 
is seen that the celloidin entered the lobule only at the tips of the veins, 
that is from the intralobular veins. The sublobular veins are clear and 
have arising from them intralobular veins which again have clusters of 
lobules attached to them. The lobules are in clusters to correspond with 
the branching of the interlobular veins. The outline of one in perspective 
is given in Fig. 34, which is reduced to a diagram in Fig. 35. 
While the hepatic lobules are irregular, anastomosing, and of unequal 
size, the portal units are regular, more spherical and of equal size. The 
Fic. 36a. Portal and hepatic veins from a corrosion preparation of the 
liver of the dog. X10. The two sets of vessels were injected with black 
and red celloidin mixture respectively, after which the liver was hardened 
in alcohol. A block of tissue was cut into very thick serial sections which 
were digested for a number of days in a solution of pancreatin at 37° C. 
After the cells were all dissolved, leaving only the connective-tisue frame- 
work and the injected celloidin the section were preserved in glycerine. 
The minutest twigs of celloidin are held in place by the delicate reticulum 
Loprils. 
branches of the portal vein are much more delicate and regular than 
those of the hepatic. A comparison between the two is shown in Figs. 32 
and 36, while the single portal branch is shown in Fig. 37. In general 
the portal branches are more regular than the hepatic, as far from them 
as possible with a tendency to run at right angles to them. The portal 
veins never come to the surface of the liver and never anastomose; the 
