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Show 1892.] BODY-CAVITY IN S N A K E S . 487 As might be expected, when this "gastric" sac is reduced in extent, what remains of it will be found at the point where it is most expanded in other cases : that is, at that point approximate to the posterior end of the stomach, where I have suggested above that search for it should be made. § IV. (iii.). The Paired Peritoneal Liver-sacs. Some writers make a point of the liver of Snakes being unilobular. This is in a sense true, in so far as, with the exception of the oft-quoted liver of Typhlops [in which animal there are some three principal, besides minor, lobulations of the liver on each side], and the trifling lobulation that may be seen in some other cases (Vipera berus and arietans), the liver of Snakes presents at first sight the appearance of one elongated body. However, morpholoyically, no animal has a more obviously bilobed liver. And it is most certainly incorrect to say, in the language of one of our text-books, that the liver of Snakes corresponds only to the right liver-lobe of other Reptiles. As Retzius remarks of the Python [(1) p. 96, (2) p. 520], the liver is divided " into a right and left half. . . each lateral half of the liver is enclosed in a serous capsule of its own." It need perhaps hardly be added that the dorsal and ventral lines of demarcation between the two halves of the liver really represent the lines along which that organ meets the median longitudinal septum, which in its dorsal part supports the oesophagus and which, in all air-breathers, divides the pulmohepatic part of the pleuroperitoneal cavity into right and left halvesl. W e shall return later, § VII., to these liver-sacs, so that little need be said of them here. They fit the liver-lobes pretty closely, and therefore cannot possibly be missed even in the smallest Snakes. In the rare cases in which the right liver-lobe tapers off along the course of the posterior vena cava (Liophis meremii, Vipera arietans and nasicornis, and Crotalus durissus), the liver-sac of that side necessarily does so too, wherefore it is hard to ascertain exactly where it ends. § IV. (iv.). The Unpaired " Omental" or " Lesser Peritoneal " Space of the Riyht Side 2. This space is practically the most difficult of any of the peritoneal spaces to find. Moreover, I do not think that it is present in the 1 Owing to the marked tilting of the liver over to the right side in Snakes, while the right, and usually only, lung often takes up a position in the mid-dorsal line, what is morphologically the median sagittal plane of the Snake, so far as the ccelom and viscera are concerned, usually, in the region of the liver, makes an angle (varying from 45° [cf. Plate XXVIII. fig. 2 B] to 90°) with the plane joining the vertebral column with the middle of the ventral scales. 2 The space referred to occurs apparently in all the Amniota, and it is, I |
