486 LEWIS DAVIS 



Data have been obtained in this study supporting the view 

 that the troublesome local reactions encountered with horses in 

 diphtheria treatment may be largely attributed to the method of 

 controlling the hydrogen ion concentration of the toxin bouillon. 

 It is a fact that in the use of the toxin under observation, prac- 

 tically no local reactions have been experienced. It is also true 

 that adjusting the toxin bouillon by the colorimetric H ion method 

 discussed above requires considerably less alkali than the use of 

 the inaccurate "hot titration" method formerly employed. 

 Whether it is the decreased amount of alkali used or possibly a 

 diminished content of toxone bodies in the final toxin which is 

 responsible for the favorable results must be left for further 

 study. 



Consideration of the foregoing production results would not 

 be complete without data showing the antitoxic response to in- 

 jection of the diphtheria toxin in horses. In the final analysis, 

 this detennines the utility of the toxin and consequently, the 

 value of the methods and culture medium which are recom- 

 mended. A summary has been prepared in the succeeding table 

 to show the potency of the antidiphtheric serum obtained in the 

 first yield from horses immunized during the past year with the 

 toxin under discussion. The first large scale bleeding has been 

 chosen for the valuation because experience has shown that the 

 potency of this serum represents more closely than that from 

 any of the succeeding bleedings the true value of the toxin in- 

 jected. 



Diphtheria antitoxin 



Analysis of the table shows that nearly 78 per cent of all the 

 new horses injected during the past year with the toxin under 

 consideration produced a serviceable antidiphtheric serum (i.e., 

 having a potency on first bleeding of 200 antitoxin units or 

 greater). Eighty per cent of the productive horses (or 82 per 



