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Show 1892.] BODY-CAVITY IN SNAKES. 479 criticism, is absolutely incorrect and misleading when he says of the Boa constrictor, " es ist kein Cavum thoracis oder abdominis vorhan-den. . . ." ; for the peritoneal cavity (" cavum abdominis ") with its various subdivisions, judging by a young specimen in the British Museum, which, by the courtesy of Mr. Boulenger, I was permitted to examine, is better seen in Boa constrictor than in most Snakes. It is, however, hardly surprising that anyone, not forewarned by allied studies, should err as to the peritoneum of these animals. I shall notice the paper by Lataste and Blanchard presently. W e are also referred to F. Leydig [" Ueber die einheimischen Schlangen," Senckenberg. naturf. Gesellschaft, Band xiii. 1883-4]. Leydig, however, like the writer in the ' Thierreichs,' who is perhaps following him, quotes indiscriminately Herring, who is wrong, and Retzius who is right ; and the conclusion which (loc. cit. p. 214) he says we may draw from the various descriptions (as to the coexistence of a peritoneal cavity and a subdivided lymph-space) is, as might be expected, vague, and does not convey a correct idea of the actual facts. To one who has elsewhere found nothing but incomplete and usually very meagre and general, if not incorrect, accounts of the Ophidian peritoneum, it is a pleasure to turn to the account of Retzius (1) & (2). This author in 1830 described the state of things in the Python, overlooking no division of the peritoneal cavity; though in the case of two of the smaller spaces he simply calls them " serous canals." His description of the peritoneum appears to be as complete as it is possible for such a description of the anatomical features of any one animal to be, without the light thrown by comparative anatomy and development. One small division of the peritoneal cavity, which embryology shows to be a remnant of the " omental" space, I did not myself discover-in any adult Snake until after reading Retzius' account of the Python. But although this careful " old master " seems to have seen more than any one else since, I nevertheless hope that there will be something " new " in the following paper, in so far as a study of their mode of origin furnishes material for the discussion of the true nature and the homologies of the various peritoneal spaces, and in so far as a comparative study of examples of nearly all the families of Snakes enables me to state it as probable that most, if not all Snakes, while differing considerably in other respects, are essentially alike in their peritoneal cavities *. W e come now to the papers by Lataste and Blanchard (3) and Blanchard (4). The statement on p. 95 of (3), to the effect that the peritoneum does not extend anteriorly to the gall-bladder, is qualified by one on p. 106, to the effect that there are two serous 1 For instance, Tupinambis (Pejus) differs strikingly from other Lizards in the possession of a most distinct transverse septum behind the liver (see Proc. Zool. Soc. 1889, plate xlviii. and text). I have recently discovered a previous mention of this structure by Meckel [Deutsches Archiv fur die Physiologie (Halle), Band iii. 1817, p. 218J. However, Meckel gave no figure or detailed description of this septum. 33* |