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Show 1 9 0 6 .] RESPIRATORY SYSTEMS IN THE OPHIDIA. 5 0 5 It is to be noted that there is no development of longitudinal trunks running along the vertebral column in the liver-region which give off branches to the portal vein. There are a number of the branches to the portal; but each of these emerges separately from the parietes or is formed of the junction of two or three. There is no extensive fusion such as occurs in the Boine Snakes generally. I do not think that this absence of a longitudinal trunk is due to the emptiness of the blood-vessels. It seems to me to be an anatomical fact. The vena renalis advehens (text-figs. 87, 88, pp. 502, 503), as is known to be the case in other Snakes, communicates directly with the mesenteric vein underlying the gut*. Between this point and the right kidney the renal vein receives about eight branches from the parietes. In the case of the left kidney, which is nearer to the cloaca than the right, there are only five of these branches. At the anterior end of the kidney the vein distinctly ends, though at the very extremity. There is no continuation forwards such as occurs so generally (? universally) among the Boidae and occasionally (Zamenis gemonensis) among the Colubrines. Each kidney also receives a special branch from the dorsal parietes, which is not mentioned by Hochstettter in Tropidonotus. This arises from the parietes at about the middle of the kidney and from several intercostal spaces on the left side of the body, but from one only on the right. In both cases these veins closely accompany the second renal artery (reckoning from the anterior end of the kidney). Their course, however, is rather different on the two sides of the body. The vein of the left side (text-fig. 88) perforates the kidney, or rather runs between the lobules of that organ ; it ultimately joins the renal afferent vein. It is remarkable that the corresponding vein of the right side of the body is different in its relation to the veins of the kidney. It was thoroughly injected, and therefore quite easy to follow. The vein is seen to have no connection whatever with the renal afferent vein of the right kidney, but it opens without doubt into the renal efferent vein (see text-fig. 87) at a point roughly opposite to its point of emergence from the parietes. This anatomical relationship is obviously very unexpected, and it is quite possible that we have here an abnormal state of affairs. The venous system of the kidneys in Coluber corais differs in some details from that of other genera. The afferent renals, some way before they reach the kidneys, give off two important branches. One of these is to the dorsal parietes, and is a vein which is very general among the Ophidia. The other forms with its fellow of the opposite caudal, which it meets at an angle of 180 degrees, what is practically the commencement of the inferior mesenteric vein running along the dorsal surface of the intestine. * In Tropidonotus and Coluber cesculapii, according to Hochstetter (Morph. Jahrb. xix. p. 489), who thus confirms Schlemm and Jourdain as regards the former. I have found this vein in Coluber corais, in Zamenis gemonensis, and Ancistrodon piscivorus. |