An Allergic Skin Reaction to Diphtheria Bacilli. 91 



both tests agreeing therefore in about 63 per cent, of persons; 

 12.5 per cent, reacted positively and 24.1 per cent, negatively to 

 both tests. 



If a positive diphtherial reaction may be regarded as an index 

 of lytic immunity, only 10 per cent, of persons were found who 

 did not show the presence of either an antitoxic or lytic immunity, 

 while 53.3 per cent, showed both types of antibodies; 24.1 per cent, 

 showed antitoxic immunity only and 12.5 per cent, allergic, but 

 no antitoxic antibody. 



4. The percentage of positive diphtherial reactions was slightly 

 greater among those who were convalescent from diphtheria. 



5. There is no relation between the occurrence of positive and 

 negative diphtherin and toxin reactions and the presence or 

 absence of diphtheria bacilli ; a negative toxin reaction in a person 

 presenting clinical evidences of infection indicates that the indi- 

 vidual does not require antitoxin but nothing more; he may be 

 infected with virulent diphtheria bacilli capable of disseminating 

 the disease. 



6. The sera of persons yielding positive diphtherin reactions 

 were not found to possess demonstrable bacteriolytic properties 

 for diphtheria bacilli. 



7. The sera of persons yielding positive diphtherin reactions 

 yielded weakly positive or negative complement fixation and 

 agglutination reactions with diphtherin as antigen. 



8. Whether or not the diphtherin reaction will prove of practical 

 value in handling outbreaks of diphtheria from the standpoint 

 of passive immunization and diagnosis will depend upon future 

 experiences under such conditions and also upon the results of 

 experimental work bearing upon the broad question of allergic 

 reactions as an index of immunity; it would appear at least that 

 more attention should be paid the question of bacteriolytic im- 

 munity in diphtheria. 



