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Show 338 MI:, K. i:. BEDDARD ox T H E [Feb. 16, the 1st and 2nd intercostal arteries ; the second accompanies the 4th ; the third and fourth the 7th and 8th respectively ; the fifth arises between arteries 9 and 10; the sixth accompanies the 14th and 15th. The next two intercostal hepatic portals correspond to the 7th and 10th intercostal arteries of the second series*. The ninth and tenth parietal veins arise respectively close to the 25th and the 28th and 29th intercostal arteries ; the tenth vein is formed by the union of two trunks. These vessels are connected with the testis. They arise from the right side. Some way behind them are two veins for the posteriorly situated testis, which arise from the parietes on the left side of the dorsal middle line. Blood-vessels of ventral parietes.-These vessels, which are numerous, are of course the equivalents of those of the anterior abdominal system in other Vertebrates. The first of them arises just opposite the 2nd intercostal artery 4 inches behind the heart. Several are accompanied by an epigastric artery, and along the ventral median line lies a continuous epigastric artery and vein of which these are branches. The first 9 of these veins open directly into the liver; they arise from the longitudinal trunk by one root or by several, A strongish arterial twig derived from the arterial plexus upon the oesophagus accompanies the first vein; but the remaining 8 have not at least a well-marked arterial companion. The longitudinal epigastric arteries, moreover, are slender in this region; there are two of them, one running on either side of the median vein ; occasionally the ax-tery breaks up into a plexus. Just before the ninth vein the epigastric artery of the right side increases in size and is shortly reinforced by the first of a series of post-hepatic epigastric branches. This first branch is the most prominent of the series. It is not associated with a vein, and divides before reaching the middle line into an anterior and a posterior branch. From the end of the hepatic series to the cloaca I counted 35 veins, which should possibly be reduced by 2, inasmuch as 2 of the veins in question were formed by the junction of two veins each. As to arteries, I counted 24 after the particularly well-developed one to which attention has just been called, and these for the most part were accompanied by veins. The number is probably understated, owing to inefficient injection posteriorly. The agreement with the corresponding veins is often very close, the artery bifurcating at the same time that the vein bifurcates. ZAMENIS FLAGELLIFORMIS. The right aortic arch divides, of course, into the aorta and an anteriorly running trunk, the anterior vertebral artery. Of these two branches the vertebral is the more important, and the aortic trunk joins it as if it were a branch entering it from behind, rather than if the vertebral were itself a branch of the aorta. * See p. 333. |