NOTE ON THE PERSISTENCE OF THE RIGHT POSTE- 

 RIOR CARDINAL VEIN IN X EN OPUS LAW IS, AND 

 ITS SIGNIFICANCE. 



By Rein HOLD Johannes Ortlepp, M.A. 



(JVith one text figure.) 



(Read July lo, 191 8.) 



Material. — The subject of this note is an adult specimen of a 

 female Xcnopus kcvis, obtained in the vicinity of Johannesburg, 

 to which my attention was drawn during a demonstration lesson ; 

 unfortunately some of the internal organs had been removed, so 

 that all the details of the smaller veins to the urino-genital system 

 could not be clearly made out. 



Morphologx. — On examining the specimen, I found that the 

 venous system was abnormal, in that the postcaval was completely 

 absent, except for that portion which lies between the kidneys, 

 and that an extra vessel, corresponding in position and function 

 to one of the post-cardinals in fishes, was present. 



Arising from the posterior medio-ventral aspect of the suius 

 venosus, there was a short vein which, soon after its origin, 

 divided into a number of small branches, which were distributed 

 to the liver lobes. Normally, the hepatic veins join with a median 

 vein — the postcaval — arising from between the two kidneys, and 

 j)assing forwards to enter into the sinus venosus. In this speci- 

 men, however, there was no vein corresponding to the precaval, 

 and consequently all the blood which passed througii the renal- 

 portal system had to be conveyed to the sinus venosus by a 

 different vessel, which normally is absent in the adult. 



This vein — the right posterior cardinal — arises from between 

 the two kidneys, receiving blood from the same by a series of 

 lateral veins, revehent renal veins ; on reaching the anterior ex- 

 tremity of the kidneys, it turned sharply to the right, passed 

 forwards, and became confluent with the right precaval at the 

 origin of the subclavian vein. 



The interrelationships of the various vessels and adjacent 

 structures are shown in the figure. 



From Dreyer's (1914-15) description of the anatomy of the 

 tadpole of X. Iccvis, it appears that both the postcardinals as well 

 as the postcaval are present ; but as the fate of these three veins 

 during later metamorphosis has not been worked out, one can at 

 present only suggest that, normally, the two postcardinals dis- 

 appear, whilst the postcaval grows in importance, and eventually 

 comes to take on all of the work done by the i^ostcardinals, as is 

 the case in common European frog. 



In the specimen under consideration, something approaching 

 the reverse seems to have taken place, in that one of the post- 

 cardinals, as well as the postcaval is completely suppressed. 



