318 CLINICAL BACTERIOLOGY. 



sibility wanting, and the manifestations of this stage can 

 not be dependent upon the virus in a living form, or at least 

 capable of multiplication, and infectious. In the case of 

 hereditary syphilis the virus is taken up by the blood, and 

 the primary lesion, which ordinarily indicates the portal of 

 infection, is wanting, and the disease sets in at once with 

 the secondary manifestations. 



Immunity. All ages and all races are equally suscep- 

 tible to syphilitic infection. Natural immunity to the disease 

 in human beings does not exist. Syphilis is characterized 

 by a marked tendency to relapses, which often appear after 

 long periods of latency. On the other hand, one attack of 

 the disease confers protection against subsequent attack 

 that is, it gives rise to immunity. Renewed infection (rein- 

 fection) occurs even after disappearance of all previous 

 morbid manifestations only exceptionally. 



According to a law laid down by Colles, the mother who 

 gives birth to a child syphilitic through the father, without 

 herself being attacked, is rendered immune by the fetus. 

 By analogy with other immunizing procedures, it is easy to 

 understand that the disease-germs do not pass over from 

 the child to the mother, so that the mother is not infected, 

 because the placental barrier is impassable to the microor- 

 ganisms, but that, on the contrary, the toxins dissolved in 

 the blood pass through this barrier from the child into the 

 maternal circulation, and thus confer immunity upon the 

 mother. The mothers of syphilitic children are actually 

 immune. They may nurse their offspring at the breast 

 without being infected, whereas healthy nurses nursing the 

 same children would be infected with syphilis. Such 

 mothers are thus certainly immune. The only point for 

 discussion is whether they have been immunized by the 

 children. According to the view of a number of syphilog- 

 raphers, they are immune because they have been, or are, 

 themselves syphilitic. Their condition of health is only 

 apparent. We shall return to this point later, in the dis- 

 cussion of heredity. According to the view just expounded, 

 immunity to syphilis would always be acquired through 

 previous infection. 



The specific therapy of syphilis has never been essen- 

 tially cleared up. Whether potassium iodid and mercurials 

 operate by destruction of the infecting microorganisms as 

 seems the more probable or by immunizing infected indi- 



