IMMUNITY IN SYPHILIS. 651 



is difficult to differentiate from variations in the 

 virulence of the infecting agent. Syphilis is said 

 to be particularly virulent when introduced into 

 a race of people for the first time. 



There is no reason to believe that natural im- immunity. 

 munity to syphilis exists in man. It was formerly 

 believed that the fact that many prostitutes who 

 were exposed to syphilis over a considerable length 

 of time and who at no time showed active symp- 

 toms, were immune to the disease. The finding 

 of positive Wassermann reactions in a large per- 

 centage of such individuals would indicate, how- 

 ever, that they did acquire syphilis. Through the 

 application of the Wassermann test, it has also 

 been shown that the laws of Colles and Profeta 

 are also incorrect. The former states that the 

 mother who gives birth to a syphilitic child with- 

 out herself showing signs of the disease, is immune 

 to syphilis. Knopfelmacher and Lehndorf ob- 

 tained positive Wassermann reactions in 56 per 

 cent, of such mothers. Profeta's law states that a 

 healthy child, born of a syphilitic mother, can 

 suckle the mother without becoming infected. In 

 this case many of the so-called healthy children 

 have been found to be syphilitic, and others which 

 were actually non-syphilitic have been observed to 

 contract the disease from the mother. 



Eegarding second infections, experiments on 

 apes have shown that second infections are readily 

 produced at any time after the primary lesion has 

 developed. Such infections are possible even after 

 thorough courses of treatment terminating in re- 

 covery. These second infections differ from the 

 first in that the incubation period is shorter and 



