OCR Text |
Show 362 Mil. 1". E. BEDDARD ox THE [Feb. 16, conditions observable in the spermatic arteries. The anterior kidney has but two arteries, of which the first arises in front of the first renal artery of the posterior kidney. The second artery of the anterior kidney arises exactly opposite to the fourth renal artery of the opposite kidney. The posterior kidney has six arteries, which, with the exception of the first, lie between the inferior mesenteric and the ensuing intestinal artery. There is finally an artery to each ureter, of which that to the posterior kidney lies after the fourth intestinal artery. PYTHOX SPILOTES. In this Snake the anterior vertebral artery is of much less calibre than the right aortic arch, of which it is obviously a branch, and not, as in Zamenis flagelliformis (see p. 338), practically its main continuation. It runs up very close to the head before becoming imbedded in the body-walls. It disappears from view only 3 inches behind the tip of the snout. Its branches are regularly intervertebral, and therefore numerous; the most striking difference which the artery in this snake shows from that of Zamenis and many other snakes, is the fact of the existence of a branch which may be termed the j^osterior vertebral artery. This is the first branch of the vertebral artery, and is given off immediately after the origin of the latter from the aortic trunk at a distance of 1 cm. from the aortic arch ; it has therefore very nearly a separate origin from the aorta. This trunk passes back along the middle line of the body, closely apposed to the parietes; it receives on the one hand the intercostal arteries which arise from the aorta and gives off, on the other, a series of branches which run to light and left and which are, I take it, the equivalents to the branches of the intercostals in many other snakes * which run also right and left. The existence of this superficial posterior vertebral artery is a further extension of the longitudinal system of trunks which is so characteristic of the Ophidiaf. This longitudinal artery is not, however, limited to the " thoracic " region ; with interruptions it continues considerably farther. The superficial artery ends at a point just about opposite to the commencement of the liver, during which space (of 7 or 8 inches) only two arteries from the aorta reach it. After this point and from it to the end of the liver I counted seven intercostal arteries arising from the aorta. Each of these on arriving near to the dorsal middle line of the body divides and runs forwards and backwards as a superficial vertebral artery, giving off paired branches as usual which penetrate the parietes ; the successive superficial arteries are so arranged with reference to each other that they leave no vertebra unsupplied-that is to say, one commences immediately after the end of another. A variable number * Hopkinson & Pancoats (loc. cit.) do not figure intercostals at all, and Jacquait does not represent the secondary connections as occurring in the species examined by him. t F. g., Hamadryad or. p. 353. |