| OCR Text |
Show slightly better developed on the right side than on the left in P. molurus. This vein ran nearly to the cloaca. It is connected by numerous branches with the renal afferent up to the point where the latter reaches the kidney; but after that point there are 110 more branches to the renal afferent until the latter leaves the kidney anteriorly. Here the vessel is connected with he anterenal prolongation of the renal afferent by one branch, or rather ends in it, for the lateral dorsal is not itself prolonged beyond the kidney, although numerous intercostal veins arise separately in front of the kidney and join the post-cardinal, as I regard this forward prolongation of the afferent renal. The absence of any intercostals running from the parietes in the region of the kidney across that gland to the renal afferent vein, such as are met with in Erythrolamprus and Coluber*, may prove to be a distinguishing feature of the Boine Snakes. Python regius may be an exception. In an injected example of that snake, the renal afferent vein was seen to receive from the parietes a branch just behind the kidney and one a little way in front. Just behind the latter, and therefore arising from the parietes just in the kidney-region, was a vessel of which I could not detect the ending. It may, however, very well have reached the post-cardinal in front of the kidney. In this species there is 110 continuous lateral vein in the kidney-region. And as the specimen was well injected in this region, I am confident of this difference from P. molurus. Azygos Vein.-The azygos vein in Boa diviniloqua is in many respects much like that of other Snakes-that is to say, it is not very extensive, extending down the body not much beyond the beginning of the liver. It gives off branches of two kinds, both of which are not always developed in Snakes, or are, at least, not always visible in examples which I have dissected. These branches are firstly those which flow from the body close to the median ventral line, on the right side of the vertebral column of course, i. e. on that side which the azygos lies upon. Besides these there is a series of veins which run so superficially to the lateral parietes as to lie actually above the surface of the body-wall. They are supported by membranes, and are not in close connection with the parietes. Two of these veins arise from the main azygos trunk before the latter reaches the level of the parietes. The main trunk of the azygos divides into two branches soon after the region of the heart. An outer branch runs back for some distance before again approaching the median line and giving branches to the intervertebral spaces. These branches generally are fewer than the intercostal spaces, and they must therefore divide within the parietes. The azygos, then, of this species supplies two regions of the body. It draws blood from the parietes in the immediate neighbourhood of the dorsal median line, and also from the body-wall 3 1 2 Mil. F. E. BEDDARD ON THE VASCULAR AND [M a y 1 , * See p. 502 (text-fig. 87) and p. 603 (text-fig. 88). |
