XII VASCULAR SYSTEM S20 
with the corresponding posterior cardinal; the left, on the con- 
trary, has ceased to be continuous with the greatly reduced left 
posterior cardinal and forms a renal portal vein, the distribution 
of which is, however, restricted to the hinder portion of the left 
kidney (Fig. 190). As in Amiurus, a branch of the caudal vein 
forms one of the tributaries of 
the hepatic portalvein. In the 
Cod it would therefore seem 
that only a relatively small 
proportion of the caudal blood 
flows through the imperfectly 
developed renal portal system, 
the bulk of it traversing the 
right posterior cardinal and 
passing directly to the heart, 
leaving, nevertheless, a modi- 
cum for transmission to the 
liver. Finally, it may be 
mentioned that in some Teleosts 
the caudal vein retains its em- 
bryonic continuity with one, 
usually the right, posterior 
cardinal, without giving off a 
renal portal affluent, as in the 
Perch (Perca fluviatilis); or, 
after division, with both pos- 
terior cardinals, as in _ the 
Lump - sucker (Cyclopterus 
lumps). In such instances as Fic. 189.—Renal portal system in the Tench 
these no portion of the caudal (Tinca vulgaris). d.c.v, v.c.v, Dorsal and 
blood traverses the kidneys, apa tare bora p eee ea 
~p.c, le an righ posterior caraina 
and if a renal portal system veins ; p.v, hepatic portal vein ; r.p.v, 
: renal portal vein; sy.v, sg.v’, segmental 
exists at all, the only true veins, (From Jourdain.) i 
renal portal veins are the ad- 
jacent segmental veins, which transmit venous blood directly to 
the kidneys, instead of first uniting with renal portal branches of 
the caudal vein as in the Tench and the Eel. 
Whatever may be the condition of the renal portal system, all 
the renal blood is eventually collected by renal veins and conveyed 
to the posterior cardinals, which are often connected by one or 
VOTES VALE Y 
hanes DU 
