128 SPECIAL HISTOLOGY. 



The diameter of the capillaries is, in general, somewhat less than 

 that of the hepatic cell-network, though relatively considerable ; 

 in man it is, on the average, 0-004 — 0'0055 /,/ , 0-002 — 0-01'" in 

 extreme instances; the wide vessels being more especially 

 found in the neighbourhood of the afferent and efferent veins, 

 the narrowest in the interval between them. The meshes of 

 the network correspond, of course, in form, with the hepatic 

 cell-network, and are thence more elongated in the interior 

 of the hepatic islets, more rounded externally, whilst their 

 breadth corresponds with that of the columns of the hepatic 

 cells, being about 0-006 — 0-02'". 



The hepatic veins essentially resemble the portal vein, in 

 so far as they possess no valves, branch out at acute angles 

 and do not anastomose ; their larger branches also receive 

 numerous minute vessels, but these lie isolated in special 

 canals in the hepatic substance to which they are firmly 

 attached, whence they do not collapse when cut across, and, 

 at least in their finer ramifications, possess no external in- 

 vestment of connective tissue, which is indeed but very rudi- 



Fig. 223. 



mentary, even in the largest trunks. The relations of the 

 ultimate branches of the hepatic vein, termed by Kiernan 

 intra-lobular veins, and by Krukenberg, vena centrales lobu- 

 lorum, are, however, totally different from those of the portal 



Fig. 223. Segment of a very successful injection of the hepatic veins of the 

 Rahhit, x 35. One vena-intralobularis is visible in its entire course, but only 

 the radicles of the other. The capillaries of the lobules partly coalesce and, in one 

 place, two venous radicles do so. 



