SECT. 162.] VESSELS OF THE LIVER. 35 I 



only one hepatic islet, but always two, or even three. Their ulti- 

 mate twigs, rami lobulares (Kiernan), penetrate, to the number of 

 ten, fifteen, or twenty, and mostly at right angles, into the neigh- 

 bouring lobules, and immediately break up into the capillary 

 network, without, in man, being in direct connection with each 

 other. Anastomoses of the portal branches are extremely seldom 

 met with (L.Beale), their ramifications being connected only by 

 the finest vascular network of the organ. 



The capillary network of the hepatic islets completely fills up 

 the interspaces of the hepatic cell-network, so that the secreting 

 parenchyma of the liver consists only of two elements, the hepatic 

 cells and the blood -capillaries. Just as the hepatic cell -network 

 forms a connected whole throughout the liver, although it is divided 

 into numerous minute patches by vessels which enter into, and 

 gall-ducts, which issue from it regularly at stated distances; so also 

 the capillary network of the blood-vessels, passes from one hepatic 

 lobule to the other, although it presents interruptions at certain 

 places. The width of the capillaries is generally somewhat less 

 than that of the hepatic cell-network, but still proportionally 

 considerable, being, in man, o - oo4'" to o*oo55"', on an average, 

 0'002'" to o'Oi"' in the extremes ; and the wider vessels are situated 

 especially in the neighbourhood of the entering and departing 

 veins of the lobules, the narrowest in the middle between the two. 

 The meshes of the network correspond, of course, to the form of 

 the hepatic cell-network, and are, accordingly, more elongated in 

 the interior parts of the lobules and more roundish towards the 

 circumference, whilst their breadth equals that of the trabecule 

 of the hepatic cells, and amounts to 0006"' to 0*02". 



The hepatic veins essentially resemble the portal, in so far as 

 they have no valves, ramify in an arborescent manner at acute 

 angles, do not anastomose, and receive along with larger branches 

 a number of small vessels. On the other hand, these veins lie 

 apart from the other vessels, in special canals of the hepatic 

 substance, and are firmly connected with it, so that, when cut 

 through, they do not collapse, and are destitute, at least in the 

 finer ramifications, of an outer covering of connective tissue, which 

 is but very slightly developed even in the largest trunks. But 

 the relations of the ultimate branches of the hepatic veins, which 

 Kiernan calls vence intralobulares, and Krukenberg, vence centrales, 

 is quite different from that which the vena portce presents. These 

 intralobular veins, 0012'" to 0'03'" in diameter, in man, it is best 

 to studv first in some animal whose liver is divided into isolated 



