OCR Text |
Show 1904.] CIRCULATORY SYSTEM IX THE OPHIDIA. 337 the artery to the anterior testes for the supply of the fat-body, two twigs are given off from the longitudinal vessel just in front of the posterior testes which also supply the fat-body. This blood-supply has been already referred to in writing of the arteries of the fat-body. Arteries of Fat-Body.- Each fat-body, which is not particularly well developed, is enclosed in a separate coelomic space. It reaches from just behind the liver to about the end of the first third of the more anteriorly-situated kidney. The longitudinal artery does not, however, so far as I can ascertain, run through the entire length of the fat-body. The main artery of the fat-body arises from the aorta far back, exactly between the posterior testis and the anterior kidney, just in front and to one side of the posterior rectal artery. It gives off a minute branch, which runs forward and belongs to the system of vessels supplying the vas deferens. It then divides into two equally stout branches, which supply respectively the anterior and the posterior region of the fat-body. The division of the artery takes place some way before it reaches the fat-body itself. The posterior branch ends posteriorly with the fat-body; the anterior branch extends forwards to the superior mesenteric artery which it joins. The longitudinal artery of the fat-body also receives another strong branch from the aorta in front of the posterior mesenteric and between it and the other testis*. A more slender tributary arises from the first of the testicular arteries supplying the anterior testis, and a second from the region of the posterior testis. The fat-body artery has thus three main origins and two less important ones. The longitudinal trunk along its course gives off repeated branches to the lobes of the fat-bodies on both sides and also epigastric branches, the number of which will be referred to under the description of the epigastric system. Anteriorly to the origin of the fat-body artery from the mesenteric artery the fat-body is supplied by a series of branches of the various visceral arteries. The longitudinal vein of the fat-body (anterior abdominal) closely accompanies the artery; it finally joins the main portal trunk in the region of the mesenteric artery. Intercostal Veins of the Portal Systems.-In the anterior region of the body, in front of the heart, there are a series of intercostal veins which pour their blood directly into the heart through the vertebral and jugular veins. In the thoracic and abdominal regions are other intercostal veins, -which are connected with the portal system of the liver and of other viscera. The first few, and they are indeed very few, belong to the hepatic portal system. They vary, as do the intercostal arteries, as to the side of the median dorsal line from which they arise. The first six of these vessels arise from the left, the next two from the right side. There are, in fact, only eight of them. The first arises between * It is noteworthy that the two chief arteries of the fat-body arise on different sides of the aorta. PROC. ZOOL. Soc-1904, VOL. I. No. XXII. 22 |