140 APPLIED IMMUNOLOGY 



made in using it as a guide to treatment than as a 

 diagnostic aid. Border-line reactions giving very- 

 slight inhibition of hsemolysis (5-10 per cent.) when 

 performed for diagnosis should be regarded as nega- 

 tive. But such a result in a case that has been known 

 to have had syphilis and to have been under treatment 

 indicates that fm^ther treatment is required. 



Occasionally in a case of late or treated syphilis 

 giving a negative Wassermann reaction, a positive re- 

 sult may be obtained immediately after a so-called 

 provocative dose of salvarsan, neosalvarsan or mer- 

 cury. It is believed that the treatment in such cases 

 is just sufficient to stimulate the spirochsetse without 

 causing their death. 



In view of the fact that treatment hy mercury or 

 salvarsan often produces a negative reaction in cases 

 where it otherwise would he positive, the test should 

 not he performed on a patient unless all treatment has 

 heen discontinued for at least three weeks. If this 

 precaution be not observed, negative results will fre- 

 quently be obtained in cases that should be positive, 

 greatly to the surprise and chagrin of the practitioner. 



In employing the Wassermann reaction in differ- 

 ential diagnosis, it must be remembered that a positive 

 result does not necessarily mean that the lesion in 

 question is syphilitic, but that there is syphilitic infec- 

 tion in the body of the patient. 



