278 A Study of the Structural Unit of the Liver 
cross d into the field Z. In fact, there is quite a regular crossing of 
portal and hepatic veins in many portions of the liver, and it indicates 
that at one time the main stems were the only vessels in that portion of 
the organ. 
I shall not venture to describe the growth of the vascular system of 
the liver in three dimensions of space, but refer the reader who desires it 
to a good double (portal and hepatic) corrosion with the diagrams given 
in Figs. 39 to 43. If he takes the pains to apply them to double corro- 
sions of the livers of very young and of old animals, I think he will find 
them of some aid. I wish, however, to add two points. First, if the 
vessel, b, Fig. 40, is imagined cut transversely, as represented in Fig. 1, 
it will be seen that the lobule represented by it must have arisen from 
three adjoining lobules. Secondly, if the tip of the lobules 7, 2, etc., are 
considered in three dimensions of space it will be found that the growing 
part of the lobule is always at a certain point, which is as far as possible 
from both portal and hepatic tips, and is marked n in Figs. 1 and 38. 
In the diagrammatic section, Fig. 1, it is seen that there is a special ar- 
rangement of the capillaries passing towards this point, and since it is so 
constant, can be located in any lobule and is of such great morphological 
significance I shall term it the nodal point of the lobule. The nodal 
points are always located in Kiernan’s interlobular fissures, but the fis- 
sures are not always nodal points. In Fig. 38 a line drawn through the 
letters ¢, n, e, n, c, n, ec marks the middle of a Kiernan fissure, but only 
the points marked n are nodal points. 
MEANING OF THE NopAL Pornts. 
In general, it is stated that the capillaries of the lobules of the liver 
radiate from the central vein and in so doing branch until the periphery 
of the lobule is reached where they communicate with the plexus of inter- 
lobular veins, as described by Kiernan. It was shown, however, by 
Krukenberg and others that the terminal portal twigs do not anastomose 
and this in itself indicates that the usual description of the capillaries of. 
the lobule is incorrect, for there must be some kind of collecting system 
for that portion of the periphery of the lobule devoid of veins. Correct 
illustrations of the vascular arrangement of the lobule in cross section 
are given by Stohr and Bohm and von Davidoff without any description 
of them in the text. 
A careful study of the vascular arrangement of the lobules will show 
that the capillaries themselves are the collecting vessels due to their own 
anastomosing system. A diagrammatic representation of this system in 
