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Show 5 0 6 MR. F. E. BEDDARD ON THE VASCULAR AND [May 1, That this vein originates from the afferent renal has been shown by Hochstetter and myself in other Snakes*. The afferent renal runs along the margin of the kidney and only dies away at the very end anteriorly. It is distinctly not continued forwards as in the Pythonidae, or if so by the minutest of twigs. In the case of the right kidney, the renal afferent receives affluents from the dorsal parietes along its course upon the kidney. The existence of affluents occupying this position seems in the present state of our knowledge to be a distinctive feature of the Colubrine Snakes as opposed to the Boidae +. These affluents are two in number. The first is near to the posterior end of the kidney, and is formed by the junction of two intercostal veins. The second is at the end of the first third of the kidney, and seems to arise from only one intercostal space. These veins join the main trunk of the afferent renal; they do not plunge independently into the kidney-substance, as they apparently do in Erythrolamprus. I could find no corresponding veins upon the opposite side of the dorsal middle line supplying the left kidney. The efferent renals do not retain their independence until they are free of the region occupied by the kidneys. The two vessels join at the anterior end of the left kidney, which is situated, as in other Snakes, behind the larger right kidney. The anterior part of the conjoined renal efferents, which is of course the vena cava inferior, received twigs from the right kidney. It is to be noted that in both cases the branches flowing from the kidneys into the venae renales efferentes have a free course of some millimetres after emerging from the kidney-tissue. Hepatic Portal System.-The portal vein receives very few affluents from the parietes before it reaches the liver. Directly after reaching the liver the portal trunk shows a spiral twisting, such as is figured by Hochstetter + in the case of the portal vein of Lacerta, just before entering the liver. As in other Snakes, the portal runs to the extreme anterior end of the liver. The affluents of the vein are, as usual, dorsal and ventral. The dorsal affluents are mainly in the region of the liver. In fact I could find only one dorsal parietal vein before the liver is reached. This vein, which springs from three intercostal spaces, joins the portal in the region of the gall-bladder, and corresponds in position with the first mesenteric artery. It is apparently general in Snakes for a vein to exist in this region. In the course of the liver, the portal receives seven or eight twigs from the dorsal parietes, which all arise from the left side of the vertebral column. These are roughly at equal distances. The one nearest the posterior end ol the liver, situated at about the beginning of the posterior third of the liver, arises by three roots from the parietes. * Hochstetter, Morph. Jahrb. xix., and supra p. 505 footnote. f See infra, p. 509. But in JEunectes (P. Z. S. 1906, vol. i. p. 21) we may find an exception. It seemed to me that in this snake an affluent vein entered the kidney as in Oplnsaurus (r. Z. S. 1905, vol. ii. p. 477). J Morph. Jahrb. xix. pi. xvi. fig. 14. |