OCR Text |
Show 488 ON THE VASCULAR SYSTEM OF LACERTILIA. [Nov. 28, They very largely arise in common with intercostals. I hey do not, however, show the continuous symmetry and regularity that is shown by the renal arteries in Ophisaurus. In Amphisbcena cinerea, v. Bedriaga states the presence of 5-7 pairs of renal arteries, of which the first pair are much the largest and are traceable for a long distance along the outer border of each kidney. The intercostal arteries in Amphisbcena are upon the Lacertilian plan, and not upon that shown in the Opliidia in spite of the length of the body. They are paired equisized arteries*, each artery of a pair close together in their origin from the ventral surface of the dorsal aorta. Though these pairs are regular and repeated with no variation from segment to segment, there are nevertheless occasional, but very occasional, indications of a divergence in the direction of the arrangement so characteristic of the Opliidia other than the Boidse. In one case, on the left side of the body, a single intercostal artery bifurcated immediately after its origin from the aorta and supplied two intercostal regions, one in front and one behind. In another case an intercostal was wanting on the left side, but a branch from the right corresponding intercostal was seen to pass under the vertebra and to supply the left side of the body. Very generally the intercostals branch before becoming lost to sight within the muscles of the dorsal parietes. There are two divisions which burrow, and a trunk which runs superficially outwards between the ribs. This superficial trunk is to be seen in other Lacertilia, particularly among the Scincidfe. No intercostals arise from the left aortic arch, which is, indeed, free from branches of any kind. Three pairs arise from the right aortic arch. Lungs.-The trachea and lungs of the present species differ very considerably from those of Amphisbcena fuliginosa, described and figured by Wiedersheim f . That author figures the lung as extending considerably anteriorly to the heart, and the trachea, opens into it by a series of short branches of its lower surface. The arrangement, in fact, is obviously suggestive of the " tracheal lung " of certain Snakes, and especially of the genus Ophiophagus, where, as I myself have recently described, the trachea opens by a series of orifices into the pre-cardiac portion of the lung X- An almost exactly similar specialisation in a Snake, or rather in many Snakes and in a snake-like Lizard, is very remarkable. It seems possible, in view of the fact that the tracheal lung exists in Snakes of quite different families, and that it also exists in Amphisbcena fuliginosa §, that this state of affairs is primitive and is to be referred to an Amphibian ancestor in which the lung, as in the Frog <fec., opens at once into the pharynx without the intermediation of any length of trachea. * V. Bedriaga, however, figures the first few intercostals as arising in an irregular and therefore snake-like fashion. f Vergl. Anat. Wirbelth. 2nd ed. 1886, p. 558. X P. Z. S. 1903, vol. ii. p. 322. § Smalian. however (Zeitschr. wiss. Zool. 1885), does not find this arrangement. |