1892.] BODY-CAVITY IN SNAKES. 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, morphologically, no animal has a more obviously 

 biiobed liver. And it is most certainly incorrect to say, in the 

 language of one of our text-books, that the liver of Snakes cor- 

 responds 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 caj)sule 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 pulraohepatic part of the pleuroperitoneal 

 cavity into right and left halves \ 'VYe 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, Fipera 

 arietans and nasicornis, and. Croialus 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 Right Side ^. 



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 coelom and viscera are concerned, usually, in the region of the 

 liver, makes an angle (varying from 45° \cf. Plate XXVIII. fig. 2 =] 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 



