ON A SPECIES OF TREPONEMA FOUND IN RABBITS 



HANS ZINSSER and J. G. HOPKINS 



From the Department of Bacteriology, College of Physicians and Surgeons, 

 Columbia University, New York 



In the course of many attempts to isolate new strains of Tre- 

 ponema pallidum from luetic rabbits, the writers have encoun- 

 tered a spiral microorganism which has appeared on six different 

 occasions in tubes prepared from the tissues of five different 

 strains of rabbit syphilis. On first observation of this micro- 

 organism it seemed difficult to decide whether it represented a 

 distinct form, or a morphological mutation of Treponema palli- 

 dum. Subsequent studies, however, have led us to feel reasonably 

 sure that the organism has no relation to T. pallidum, but repre- 

 sents a distinct species present in the rabbit tissue, which grows 

 in the tubes as prepared by the Noguchi method. It is a curious 

 fact that although innumerable tubes have been prepared by the 

 same method, in the course of the last three years, with normal 

 rabbit kidney for transplantation of pure cultures of Treponema 

 pallidum (both Noguchi's strains and our own), the microorgan- 

 ism concerning which we wish to report has never appeared in 

 such cultures but has been seen only in those implanted with the 

 syphilitic testicular tissue of diseased rabbits. We therefore be- 

 lieve it at least very unlikely that the organism had its origin in 

 the normal rabbit kidney tissue which was used in both kinds of 

 culture. Since we have not made more than a few dozen plants 

 with normal rabbit testis, we can not decide whether the micro- 

 organism we are describing may be a parasite in normal rabbit 

 testes, or whether its presence is incidental only to the abnormal 

 conditions occurring in the luetic lesions. To determine this 

 would probably require a great deal of experimentation and time 

 (to say nothing of luck), since we have encountered the organism 

 but six times in the course of three years during which many 

 hundreds of tubes were planted and examined. 



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