. The Cambridge natural history. Zoology. XII VASCULAR SYSTEM 321 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 portal vein. In the Cod it would therefore seem that only a relatively small proportion of the caudal blood flows through the imperfectly developed renal portal sys
. The Cambridge natural history. Zoology. XII VASCULAR SYSTEM 321 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 portal vein. 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 (Ferca fluviatilis); or, after division, with both pos- terior cardinals, as in the Lump - sucker (Cyclopterus lumpus). In such instances as these no portion of the caudal blood traverses the kidneys, and if a renal portal system exists at all, the only true 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 VOL. VII ^. Fia. 189.—Eenal portal system in the Tencli {Tinea vulgaris), , Dorsal and ventral caudal veins ; k, kidney ; , left and right posterior cardinal veins ; , hepatic portal vein ; , renal portal vein ; , ', segmental veins. (From Jourdain.). Please note that these images are extracted from scanned page images that
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
