TREPONEMA FOUND IN RABBITS 491 



in the fourth generation. The cultures in which it multiphed 

 were sealed with oil, and at first we found the organism near the 

 bottom of the tubes, about the kidney tissue. Subsequent study, 

 however, revealed that the most likely place to find them was 

 about one inch from the top under the oil. In such tubes the 

 growth was sometimes indicated by a very faint haziness not seen 

 without careful examination and usually not larger than the head 

 of a pin. 



In the material fished from such an area, small clumps of 

 three, four, or five spirals may be seen under the dark field as 

 depicted in the photographs. We have not yet been able to 

 purify this organism, a task of great difficulty because of its im- 

 mobility. We have not had a sufficiently profuse growth to at- 

 tain success by the dilution methods, and the first appearance of 

 the microorganism has so far occurred only in contaminated 

 tubes together with motile bacilli. The continued cultivation 

 of the microorganism has, as it were, hung on a thread, the growth 

 being very sparse and taking about a month or two to develop 

 at all. 



We have withheld the report on this organism for many 

 months because we have been unable to obtain it in pure cul- 

 ture. Unless chance favors our efforts more than heretofore, it 

 may take a year or two to achieve this, and perhaps we may lose 

 and recover it several times before this result is obtained. We 

 venture to make this brief report now, therefore, since many 

 investigators are studying the cultivation of Treponema pallidum 

 from rabbits and we have not seen any mention of a microor- 

 ganism of this kind, so easily differentiated morphologically from 

 T. pallidum, yet appearing in rabbits in the same location 

 and under the same conditions. 



Knowledge of its occurrence and its limitation, so far in our 

 experience, to cultures from syphilitic testis should be of value 

 to others working in this field. Should it eventually prove to be 

 a hitherto undescribed species, we would suggest as a suitable 

 name for it ^^ Treponema rigidum.'^ 



