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Show 1 9 0 5 .] OF THE YELLOW-THROATED LIZARD. 2 6 5 The left systemic arch gives off no branches at all that I could discover. From the right systemic arch (which joins the left at about the commencement of the lung) the two subclavians (text-fig. 37, Sci., p. 263) are given off, nearly, if not exactly, opposite to each other. In front of this arises the vertebral artery (I.e.), which gives ofl an oesophageal branch before plunging into the thickness of the parietes. Behind the vertebral artery commences the series of intercostals. The first intercostal artery arises just before the junction of the two aortae. It gives off a branch to the oesophagus. The next two intercostals have also oesophageal branches ; but it is to be noted that in all these the right intercostal alone has this oesophageal branch. The left has none. The remaining intercostals have no oesophageal or gastric branches. Their arrangement is peculiar and agrees with that of the Skinks ; it differs from that of some other Lizards. In Tropidurus hispidus, for example, the regularly paired intercostals emerge from the dorsal aorta close to the articulation of successive vertebrae, and plunge at once into the thickness of the parietes. In Gerrhosaurus the intercostal arteries emerge from the aorta at about the middle of each vertebra. In many cases, and the arrangement is roughly alternating, the intercostal of one or both sides divides at once into two branches; one of these plunges at once into the thickness of the parietes. The other passes obliquely forwards and runs superficially in close relation to a rib. This, however, only occurs in the thoracic region, not in the lumbar. Precisely the same disposition of vessels is found in Eumeces and some other Skinks, and the fact is a bond of union between the Gerrhosauridae and Scincidae. The next artery to arise from the aorta is a gastro-oesophageal (text-fig. 37, oes, g, p. 263, and text-fig. 38, ces, g1, p. 264), which divides at once into a thin forwardly directed oesophageal, and a stout backwardly directed gastric. Between this and the large gastric artery (text-fig. 38, g~) are 6 pairs of intercostals. Two pairs intervene between this artery and that of the large intestine, and one pair between the latter and the artery of the small intestine. The ovarian and oviducal arteries present some features which are worthy of note. There are three pairs of oviducal arteries which are not symmetrical. The first of these is really mainly an ovarian artery, which gives off a thin and slender oviducal branch running along the anterior section of the oviduct. The two remaining oviducal arteries arise in common with an intercostal. They lie in front of the rectal artery. Venous System. Although the venous system of neither of the examples at my disposal was injected, most of the veins were beautifully displayed by their own turgescence. |
