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Show 24 MR. F. E. BEDDARD ON THE [Jan. 16, the whole of the mesonephros, and as the blood-vessels arising from the parietes do extend along at any rate very nearly the whole of the mesonephros, as does the longitudinal vein into which they pour their contents, it would appear that these suprarenal afferent portals are also concerned with the blood-supply of the mesonephros, vid the remains of the posterior cardinal. The suprarenal portals are thus not veins especially destined for the suprarenal circulation, but originally merely the parietal branches of the cardinal. On the left side I found only three of these veins. Precisely the same series of modifications appear to have proceeded in the case of the liver and of the parieto-hepatic portals. In the Anaconda for example, and for the matter of that in all snakes, as it appears, that have been hitherto examined anatomically, the portal vein extends along the liver nearly to its anterior end. This is shown plainly in the figure of the circulatory system of the Python given by Jacquart*. Into this portal, which runs along the lower surface of the liver, open all or most of the vessels bringing blood to the liver from the parietes. In the same way in certain Lizards (for instance, Amphisbcena, Ophisaurus, and Hatteria) there are at least considerable traces of the same forward extension of the portal. Finally we get the stage which characterises the majority of the Lacertilia, so far as existing knowledge allows us to say, in which the portal enters the liver at its posterior extremity and is not continued forward as a continuous trunk. In these lizards the parieto-hepatic portal veins enter the liver directly, instead of indirectly through the portal vein. Dorsal Parieto-hepaticVeins.-These veins are entirely developed upon the left side of the body in both specimens. They are, as in other snakes, very highly developed, and a great portion of the blood of the whole body must be contained in them. I describe them only in one specimen; they appeared to be much the same in the other. The first of these veins, advancing from behind forwards, joins the portal vein about on a level wTith the extreme end of the liver, one lobe of which reaches considerably further back than the other. It is one of the largest of the dorsal parieto-hepatic veins and on reaching the neighbourhood of the body-wall divides into a forwardly running and a backwardly running branch. Just before this division the vein receives twigs from the stomach. The backwardly running branch supplies seven intercostal spaces. The forwardly running branch supplies nine intercostal spaces before the second trunk arises which joins the portal vein just in front of the end of the shorter liver-lobe. As in other snakes, the portal vein runs superficially along the liver, giving off twigs rio-ht and left to the liver itself and receiving the dorsal parieto-hepatic vessels. Of these vessels (see text-fig. 7, p. 23) I counted nine in addition to the two that have already been described. At their Ann. Sci. Nat. (4) iv. p. 321. |