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Show 198 DR. R. W. SHUFELDT ON [Apr. 1, (4) a few interlacing ducts, joined by one or two (?) hepatic ducts occurring on the surface of the gall-bladder or just near it. In figure 2, of Plate XVI., I present a drawing of the liver (and other parts associated) of Heloderma, and although in that drawing the parts are of their normal sizes and lengths they are pulled rather downwards and forwards in order to show them off better. The Spleen.-This peculiar organ is of a bright red colour in the living Heloderma, and, as in so many Lizards, is freely swung in the fold of the peritoneum known as the mesogaster. In form it is sub-ovoid, being rounded at one end and rather pointed at the other, and lies about a centimetre from the concave curvature of the stomach. It measures in length, in a large specimen of the Heloderma, 1*4 centimetre, and has a width of about 8 millimetres. A large vein leads from it which joins the portal vein, while it is supplied with arterial blood by the splenic artery, which is a branch of the dorsal aortic artery. In its position it lies upon a crossing of a number of the vessels borne by the mesogaster, but in so far as I can see they seem to have no other special connection with this organ. Very little seems to have been written about the spleen in Lizards. Dr. Giinther has said that the " spleen and pancreas are very elongate and narrow " in Hatteria l. As referring to Reptiles, the word "spleen" does not even occur in the General Index (vol. iii.) of Sir Richard Owen's ' Anatomy of Vertebrata,' and I fail to find anything definite about that organ in the Beptilia in the same work. In Rana the spleen is placed near the anterior commencement of the rectum. Turner, who is pleased to notice the great value of work done in " comparative anatomy," has not a word to say upon the comparative morphology of the spleen in his article upon the general subject of Anatomy, and in that article confines what he has to say upon the organ under consideration to a few words having reference to the anatomy of the spleen in a single type representing but a single family of the Vertebrata (Homo)". It is hardly to be expected that we shall ever possess a very complete knowledge of the physiology of this organ so long as we remain so ignorant of its comparative morphology. In this Lizard it has simply the appearance of a large, isolated lymphatic gland, and the remark of Huxley that "The spleen is substantially a lymphatic gland," may still bespeak the summation of our knowledge upon that point3. The Alimentary Canal.-In describing this we shall for the present pass by the tongue and certain other structures that pertain to the mouth-parts, and present what we have to say about them further along. The Oesophagus consists of a straight tube extending from the buccal cavity to a point opposite the apex of the heart. In its pha- 1 Giinther, " Contributions to the Anatomy of Hatteria (R hychocephalus, Owen)," Phil. Trans, pt. ii. 1867, p. 28. 2 Turner, William, Article "Anatomy": Encyclopedia Britannica, 9th edition, vol. i. (see pp. 819 and 907). 3 Huxley, T. H., ' The Anatomy of Vertebrated Animals,'p. 91. |