230 Mr Lanchester and Mr Thacker, Superior Vena Cava of the Cat 



are at present too small for us to speak with confidence on this 

 point. In this second type the Vena Cava was approximately 

 twice the length of the Innominates. 



Finally, we had one animal which was clearly in quite a different 

 class. In this specimen the Vena Cava was only 19 % the length 

 of the trachea and the two Innominates were themselves swollen 

 almost to the proportions of Venae Cavae. The mean length of the 

 Innominates was, in fact, slightly greater than that of the Vena 

 Cava. It is owing to the existence of this specimen that, notwith- 

 standing the small total number, we think the curve of variation 

 cannot be that of normal continuous variation. In view of the 

 evolution of the single Vena Cava we think that even these pre- 

 liminary results may be of some interest and, at present, they 

 would appear to be congruous with a discontinuous method of 

 evolution of the single Vena Cava condition. 



References. 



1. St George Mivart. The Gat. (1881) 



2. B. G. Wilder and S. H. Gage. Anatomical Technology as applied to the 

 Domestic Cat. (1882) 



3. J. Reighard and H. S. Jennings. The Anatomy of the Gat. (1901) 



4. A. Davison. Mammalian Anatomy with special reference to the Gat. (1903) 



5. O. C. Bradley. "A case of Left Anterior (Superior) Vena Cava in the 

 Dog." Anat. Anz. xxL pp. 142-144. (1902) 



6. R. Pearl. "An Abnormality of the venous system of the Cat, with some 

 considerations regarding adaptation in teratological development." Archiv 

 f. Entwicklungsmechanik der Organismen, xxv. pp. 648-654. (1908) 



