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Show 1888.J VEINS IN THE ANUROUS AMPHIBIA. 123 between a late-formed hepatic vessel and one or both of the posterior cardinal veins. To that portion which is derived from the cardinal veins, and which receives the venae renales revehentes, he applies the term " urniere Abschnitte"; it is represented, iu the adults of the higher forms, by all behind and including the renal veins. He further asserts that whereas in Amphibia the two posterior cardinals become confluent to form this, in Mammalia1, on the other hand, the cardinal vein of the right side also gives origin to it. On the completion of the above-named developmental processes the anterior or prerenal portions of the posterior cardinal veins either become modified, to form the azygos and hemi-azygos veins of human anatomy, or, for the most part, disappear. Hochstetter has worked out the steps in the development in Bombinator, Pelobates, Rana, and Salamandra among Amphibia. So far as Bombinator is concerned, he fully confirms the classical researches of Goette, except for the fact tbat that author failed to observe the persistence of the entire posterior cardinals in the adult. Hochstetter has shown that in Bombinator igneus their anterior portions (morphological azygos veins) not only persist for life, but that with their confluence posteriorly, to form the hinder part of the vena cava inferior, their original continuity is not destroyed. There thus result two well-defined veins (cp. of fig.), which pass upwards and forwards, side by side with the arches of the aorta, putting, as in some Urodeles, the fully formed vena cava inferior into direct communication with the veins of the anterior extremities. In Rana, according to Hochstetter, the anterior segments of the posterior cardinals atrophy during metamorphosis. A n individual example of the Common Frog (R. temporaria, adult 2 ) has, however, recently come into my hands2, in which the vessel persisted for its entirety on one side (see fig., p. 124)3. Not only so, but its development had continued pari passu with that of other related parts-in excess of that seen even in Bombinator. The drawing speaks for itself as to detail, and it must suffice to point out that, except as concerned the presence and relations of this vein, no noteworthy difference could be detected between the distribution of even the smaller vessels in this animal and those of the ordinary adult. The least normal among the veins were the ovarian ones (ov.), which, as will be seen, were strikingly asymmetrical. There was not the remotest trace of the corresponding portion of the right posterior cardinal. The persistence of this vein in one of the Ranidae is, in itself, deserving of record; but careful comparison with Bombinator has revealed an interesting difference between the two. Hochstetter confirms and extends Goette's discovery that the main trunks of the venae renales advehentes are primarily continuous with the posterior cardinals, forming trunks (Jacobson's veins) the lower ends of which, subsequently receiving the iliac veins, become the renal portals 1 Anat. Anz. vol. ii. 1887, p. 519. 2 Thanks to the diligence of m y pupil, Mr. W . F. Hume. 3 As these sheets were passing through the press I met with the same condition in a male of Bombinator bombinus. |