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Show 1895.] LUNGS OF SNAKES, AMPHISBJENIDJE, ETC. 709 carried a step farther and that the ancestors of this second, like those of the first, had some trace of a second lung. Secondly, what significance may we attach to the suppression of one or other lung ? Can we, I mean, correlate such suppression with any other anatomical or physiological characters ? As we know, there is, as a rule, on the whole a very distinct bilateral symmetry in the bodies of pulmonate vertebrates, but there is also, as is well known, one marked departure from such symmetry which appears early, with which may, I think, be correlated certain departures from symmetry in some of the other organs. I refer to the marked leaning of the stomach to the left side. "Whatever be the cause of this, w e have the fact, as also the fact that in the case of these abnormal specimens in which the position of the stomach is reversed there is wont to be a reversed position of the great vascular trunks (the aortic root and the postcaval vein) and other correlated changes. There is, then, evidently a correlation between the asymmetry of the stomach and the asymmetry of some of the other organs ; and while in some cases it may be better to say that both are due to some common cause, in other cases (and I think this difference in the size of the lungs one of them) it would seem reasonable to speak of the asymmetry of the stomach as a cause of the asymmetry in the other organ. Prom the fact, however, that only some of the animals which have the asymmetrical stomach have unequal lungs, it is obviously not by itself a sufficient cause. The leftward inclination of the stomach and adjoining part of the oesophagus only leads to inequality of the lungs when some second cause, such as the snake-like habit of the body [which naturally renders the accommodation of the viscera a work of greater difficulty], or in mammals some other cause [which I will presently suggest], is superadded. This view harmonizes with the fact that in the Amphisbaenidae [in which the left lung is the larger] the leftward displacement of the stomach is but small, while the oesophagus is sometimes markedly displaced to the right side. Of course this, as it stands, might suggest that w e had here merely a case of mechanical displacement of the oesophagus and stomach by the left lung instead of an obliteration of the right lung by the rightwardly inclined alimentary canal. But in certain of the Amphisbaenidae [e.g. Amphisbcena alba and Anops kingii, two forms with a total absence of right lung] it is clear that we have something more than this, for though we have no case of "situs inversus " of the postcaval veiu, which runs as usual on the right side, w e find that the veins from the stomach to the liver are not as usual confined to the median gastro-hepatic ligament, but run in that right dorsal ligament of the liver (the " Hohlvenengekrose" mentioned above, p. 698) which usually carries none but systemic veins, such as the postcaval and vertebro-intercostals. It is at least interesting that this, so far as I a m aware unique, feature of the vascular system, which, I take it, argues that the stomach is morphologically more to the right side than |