| OCR Text |
Show 110 MR. F. E. BEDDARD OX THE [May 17, vertebrae ; but each intercostal bifurcates close to the parietes and supplies but a single intervertebral area. The arrangement in this region of the body in fact is precisely like that figured by Jacquart * for Python sebce, and which I can confirm from my own dissections of the same serpent. In Python sebce, however, this arrangement appears to persist throughout the whole body. In Eryx, on the other hand, a little way back, a third mode of arrangement of the intercostal arteries occurs. The point of bifurcation of the single intercostal advances higher up its stem (a in text-fig. 20) until (&) a right and left intercostal is established arising separately from the aorta. A further differentiation is shown in the case of the intercostals lettered c and d in the figure referred to. It will be observed that in c the left intercostal is much thicker than its fellow and than most of the neighbouring intercostals, while in cl the vessel has become single owing to the complete disappearance of its fellow. These facts indicate the way in which the irregular intercostal arteries (sometimes right and Text-fig. 20. C d (r CL Part of intercostal arterial system of Eryx jaculus. An., aorta; a, b, c, d, intercostal arteries; C.v.r., C.v.l., right and left posterior cardinals; G., gastric artery; L ., end of liver; S.mes., superior mesenteric arteiy. sometimes left and at unequal distances) of more modified snakes have been formed. Obliterate in the accompanying drawing (text-fig. 20) the finer intercostals and leave only those of magnified calibre, and the result would be a reproduction of the intercostal system in many Colubrine Snakes. This double series of intercostal vessels in Eryx has its counterpart in Eunectes murinus. In the A naconda I find both intercostals arising singly which run for varying distances along the median dorsal line giving oil paired branches to the parietes, and regularly paired intercostals arising separately from the dorsal vessel It is important to notice the agreement in these particulars between Eryx and Eunectes and the difference from Python, since the two former belong to the subfamily Boince, and the latter, naturally, to the subfamily Pythonince. It is difficult to say which of the * Ann. Sci. Nat. (4) iv. p. 321. |
