The subject of bacterial allergy in its relation to certain phenomena of infectious diseases has assumed increasing importance in recent years. In our studies of rheumatic fever the view that such an allergy has an important bearing in the pathogenesis of the disease has become more and more prominent. Several years ago one of us1called attention to the similarity between many of the manifestations of rheumatic fever and those of syphilis and tuberculosis. The anatomic features of these last two diseases have been thoroughly established as allergic in their pathogenesis. If, therefore, one had a conception of rheumatic fever as an analogous disease, it seemed only logical to determine whether the micro-organisms suspected of playing an etiologic rôle could be brought into relationship with any allergic state. In this connection we2have been able to show that by suitable inoculation with nonhemolytic streptococci it is possible to