| OCR Text |
Show 210 DR. R. w. S H U F E L D T O N [Apr. 1, is found in the other. The latter develops the usual extra-, infra-, and suprastapedial processes, while the last-named sends off a small special apophysis of its own that lies in the epithelium lining the internal surface of the ear-drum. Mesially, the columella auris is slightly enlarged, tipped with cartilage and closely fitted into the fenestra ovalis. Upon properly opening the dense, flinty, osseous otic capsule, I find a sacculus of fair size and with the three semicircular canals disposed somewhat as they are in Lacerta. The lagena is moderately well developed, but shows barely any inclination to become spiriform. Beyond these casual observations I made no special note, in so far as the auditory organ was concerned. This apparatus widely varies in the Lacertilia, and to make correct and exhaustive dissections of these parts requires much time and abundance of material, neither of which are quite as I would have them at present. XI. A FEW BRIEF NOTES UPON THE ARTERIAL SYSTEM. Upon examining the dorsal aorta below the heart, it is seen that in its branching it is inclined to throw off rather a generous supply of offshoots. At the point where the cceliaco-mesenteric is usually given off, two arteries arise-the hepatic, which thereafter gives off smaller mesenteric branches; and, secondly, a cceliac, which chiefly supplies the stomach, the spleen, and the pancreas. About a centimetre below the point where the cceliaco-mesenteric comes away there is given off a large mesenteric branch, which with its branches furnishes the principal arterial supply to the intestine and its supporting mesenteric membrane. A few smaller mesenteric offshoots are sent forth at irregular distances below this point. Branches from these, as well as from the dorsal aorta, still more posteriorly, supply the retrahentes costarum muscles and less important structures along the region of the spine. The ovarian branches exhibit no special peculiarities. There may be as many as seven renal branches upon either side ; a generous supply of hemorrhoidal arteries are also thrown off; while a vesical branch to the bladder is supplied by the right common iliac. Posteriorly, the dorsal aorta is continued to the end of the tail as the caudal aorta, and for the entire length of this appendage it passes between the arches of the chevron bones. I made no especial research for the existence of the retia mirabilia along the caudal portion of the vertebral column in this lizard, but have reason to believe that if such vascular anastomoses there occur, in our subject, they will be found to be not very markedly developed in the region to which we have referred. It is generally understood that a rete mirabile is more likely to be discovered along the vertebral column in the tail of those forms of Lizards and Blindworms wherein that structure is often lost through some mishap and nature reproduces the appendage again. This is especially true of the Blindworms. It is not likely that our thick-tailed Heloderma often parts with that extremity of its body ; it is nevertheless true, however, that when it does, nature supplies a new tail in precisely the same manner as we see it reproduced in other Lizards similarly"gifted. |
