1914] /. Bronfenhrenner and J. Rockman 385 



sample of the tuberculin. As this would mean an increase for 

 some specimens, a decrease for others, in the concentration of the 

 active principle in the tuberculin, we attempted to find what frac- 

 tion of the bulk of the tuberculin was directly responsible for its 

 antigenic properties. 



We are obliged to Professor W. J. Gies for his valuable sug- 

 gestions as to the methods to be employed for the study of this 

 problem. Our work is temporarily interrupted on account of un- 

 foreseen conditions preventing us from getting new supplies of 

 antigen from Professor Besredka, but will be continued as soon as 

 possible* 



