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Scientific Proceedings (73). 



washed twice with large volumes of sterile salt solution. After 

 the final washing the bacilli were re-suspended in sufficient sterile 

 salt solution to make, after thorough shaking, about two billion 

 bacilli per cubic centimeter. This emulsion was heated at 6o° C. 

 for an hour; cultured for sterility and preserved with 0.2 per cent, 

 tricresol. Subcutaneous injection of 1 and 2 cubic centimeters 

 into 250 gram guinea-pigs showed absolutely no evidences of local 

 reaction or general toxemia. In conducting the test, 0.1 c.c. of 

 the emulsion which we have called diphtherin, was injected intra- 

 cutaneously in the arm. 



Reactions with the diphtherin were usually well marked and 

 of two types, papular and pustular reactions. The latter were 

 more severe than the former and both occurred with well-defined 

 zones of erythema. These reactions usually reached their height 

 within seventy-two hours and then began to recede. 



The toxin tests were conducted with one-fortieth the M. L. D. 

 of toxin diluted with sufficient normal salt solution containing 

 0.2 per cent, tricresol to render the dose 0.1 c.c. which amount 

 was injected intracutaneously. 



The throats and noses of a large number of persons were cul- 

 tured to study the relation between the occurrence of positive 

 reactions and the presence or absence of diphtheria bacilli in the 

 upper air passages. 



The bacteriolytic power of the sera of persons reacting posi- 

 tively and negatively to the diphtherin test, for living diphtheria 

 bacilli were conducted toward throwing more light upon the 

 nature of the allergic antibody. Complement fixation and 

 agglutination tests were likewise conducted. 



The following is a summary of the results of this investigation: 



1. An allergic skin reaction was observed in about 70 per cent, 

 of children and 35 per cent, of adults following the intracutaneous 

 injection of a polyvalent antigen of washed, neutralized and heat- 

 killed diphtheria bacilli. 



2. These reactions were regarded as allergic in character and 

 therefore entirely distinct from the toxin reaction of Schick. 



3. About 53 per cent, of persons of various ages yielded positive 

 diphtherin and negative toxin (Schick) reactions. About 10 per 

 cent, yielded negative diphtherin and positive toxin reactions, 



