STRENGTHS EMPLOYED 



33 



when we have stated that some of them are not 

 effective, it must be understood that we mean 

 that they are not effective in the strengths tried. 

 It is manifestly impossible to try every concen- 

 tration. We have, however, employed several 

 strengths of each substance, beginning usually 

 with 1 c.c. of a 1-per-cent solution, and then 

 halving, quartering, doubling, and quadrupling 

 the amount. 



We wish to acknowledge our indebtedness to 

 Dr. Titherley for his advice. 



