246 The Philippine Journal of Science "23 



reinfection. Our experiments on the reinoculation of clavos 

 cases suggest that latent cases are not likely to develop typical 

 granulomata. The immunity in yaws is not high in degree, 

 and one attack of the disease does not necessarily afford protec- 

 tion against reinfection. 



Cross immunity in yaws and syphilis. — In the lower animals, 

 with the exception of the higher apes, the available evidence 

 indicates that experimental yaws terminates spontaneously with 

 the primary stage. A large amount of work has been conducted 

 with the object of determining the relationship between yaws 

 and syphilis. Experiments have been made upon animals and 

 even upon man. With one exception, neither cross protection 

 nor modification of the course of either disease has been ob- 

 served. A man who had developed yaws was inoculated by 

 Charlouis with syphilis. A typical chancre and characteristic 

 secondary eruption developed. A second patient infected with 

 yaws contracted syphilis naturally, the disease running a typical 

 course in the primary and secondary stages before treatment 

 was commenced. Bahr,(2) on the other hand, noted that in 

 Ceylon syphilis and yaws do not coexist in the same community, 

 and that in Fiji yaws prevails very widely while syphilis is 

 unknown, although there is frequent opportunity for its intro- 

 duction. He considers that in man a reciprocal protection is 

 developed between the two diseases. 



Neisser, Baerman, and Halberstadter,(7) working in Java, 

 found that monkeys successfully inoculated with syphilis were 

 also susceptible to yaws, and vice versa. These findings were 

 confirmed independently by Castellani.(3) Somewhat different 

 results were obtained by Levaditi and Nattan-Larrier.(6) Mon- 

 keys infected with syphilis were protected completely against 

 yaws. The results of these experiments might well vary slightly 

 according to the stage of the disease at which the cross-inocula- 

 tions were performed. Before concluding that yaws affords no 

 protection whatever against syphilis, it would be desirable to 

 demonstrate that some degree of immunity had been established 

 to yaws itself before testing the resistance to syphilis. 



Notwithstanding the discrepancies in the clinical and experi- 

 mental evidence, the accepted opinion to-day leans decidedly to 

 the conclusion that the two species, Treponema pertenue and 

 T. pallidum, which have so many characteristics in common, do 

 not afford any substantial cross-protection. It is reasonable to 

 assume that, in the process of evolution, these two species arose 

 from a common ancestor. There is no ground, however, for any 



