Experiments with Treponema pallidum. 255 



131 (1713) 



Superinoculation experiments with Treponema pallidum. 



By WADE H. BROWN and LOUISE PEARCE. 



[From the Rockefeller Institute, New York City.] 



The majority of investigators have interpreted the results of 

 superinoculation experiments with Treponema pallidum as showing 

 that one infection affords protection against another. The chief 

 criterion for determining results has been the production of a 

 characteristic lesion containing spirochetes, it being virtually 

 assumed that if no lesion occurred no infection had taken place. 

 When it is recalled that the lesion produced at the portal of entry 

 in a first infection may be very slight or entirely absent 1 and that 

 organisms may multiply in the body for months or even years 

 without giving rise to any external manifestation of disease, it is 

 obvious that such a standard of measurement is of more value as 

 an index of the ability to produce a manifestation of disease than 

 of infection, and that infection cannot be excluded upon this 

 basis. It would appear, therefore, that before the results of super- 

 inoculation experiments can be made clear, the subject must be 

 approached from a broader point of view and that evidence must 

 be adduced which will enable one to see beyond the reaction at the 

 site of inoculation. 



With this idea in view, a large series of superinoculation ex- 

 periments was carried out on rabbits with five strains of Treponema 

 pallidum representing organisms of a wide range of virulence for 

 these animals. These strains included the highly virulent ones of 

 Nichols and of Zinsser and Hopkins, isolated in 1912 and 1913, 

 and three less virulent strains, isolated during the fall of 1919. 

 In general, the animals were first inoculated in one or both testicles 

 while the second inoculation was made intracutaneously on the 

 sheath or at the base of one ear using equivalent doses of a testi- 

 cular emulsion. The reaction to superinoculation was studied 

 from the period of early primary infection to that of latency fol- 

 lowing spontaneous healing of primary or generalized lesions in- 



1 Brown, W. H., and Pearce, L., Proc. Soc. Exper. Biol, and Med., 1921, 

 xviii, 200. 



