698 MB. GfiEAftD W. BtTTlEE ON TfiE [NoV. 19, 



As remarked above, and as is well knowoi, the lungs of verte- 

 brates are separated by one or more longitudinal septa. One of 

 these contains the alimentary canal and is the median septum, 

 marking the median plane of the body. This is composed of the 

 dorsal hgament of the alimentary canal, the gastrohepatic and 

 hepato-cesophageal membrane, and the ventral, or so-called " sus- 

 pensory," ligament of the liver. The other membrane is that one 

 which is so conspicuous in tailed Amphibians and most Lizards, 

 passing from the dorsal surface of the right liver-lobe to the dorsal 

 body-wall. This membrane which, with, its fellow on the left side 

 [which, however, except in Amphisbseuidae remains almost or quite 

 rudimentary, owing apparently to the mechanical obstacle to its 

 development offered by the laterally displaced stomach], can be 

 traced either in the adults or the embryos of other pulmonate 

 vertebrates, has under one name or another received much atten- 

 tion from those who in the last seven years have written on the 

 membranes and septa of the vertebrate body-cavity ^. We may, 

 following Hochstetter, call it the " Hohlvenengekriise " (postcaval 

 ligament), to express the idea that its hinder portion serves as a 

 bridge for the posthepatic portion of the postcaval vein ; or we 

 may call it the " right pulmohepatic hgament," to express 

 the idea that it, like its fellow of the other side when present, 

 arises in the embryo [I speak of Amniota, — Lacerta and Gallus'] in 

 connection with the development of the lung and serves to attach 

 it to the liver ; or we may call it simply the right dorsal ligament 

 of the liver. As a matter of fact this membrane, with the excep- 

 tion of its posterior portion, does not occur in Snakes as a mem- 

 brane distinct from the median or gastrohepatic, for the body- 

 cavity does not extend between the right lung and the oesophagus 

 and stomach as in Amphibia and most Lizards. It is, however, well 

 seen in many snake-like Lizards. 



I have referred to these membranous septa because, as is so 

 often the case with such membranes, they are the carriers of 

 certain definite blood-vessels, which ai-e to serve us as landmarks. 

 The morphological position of these blood-vessels in relation to the 

 various organs, and particularly to the lungs, we first of all fix by 

 the fact of their running in these membranes, whose relations are 

 so well known and clear in Lizards, and we then can use these same 

 blood-vessels as landmarks in Snakes, where the membranous septa 

 would otherwise be hardly traceable. 



Fortunately for our purpose, in Snakes, as in some elongated 

 snake-like Lizards and Amphibians, the blood-vessels referred to 

 tend to occur as series of simple vessels instead of as a lesser number 



1 R Hochstetter, "Ueber das Gekrose der hintereo HoLlveue," Anat. Ans. 

 Bd. iii. pp. 965-974 (1888). 



Eavn, Archiv fur Anat. u. Phys., Anat. Abth. 1889, pp. 123-154 & 412. 



a. W. Butler, Proc, Zool. Soc. 1889, pp. 452-474. 



H. Klaatsch, " Zur Morphologie der Meaenterialbildungen am Da rmkanal der 

 Wirbelthiere. Theil I. Amphibien u. Reptilien," Morph. Jahrb. 1892, pp. 385- 

 450. 



