334 PHARMACEUTICAL BACTERIOLOGY 



EFFICIENCY VALUE OF A FEW DISINFECTANTS 



THE WORTH HALE TOXICITY COEFFICIENT 



Worth Hale of the U. S. Public Health Service Hygienic Laboratory 

 has worked out a method for determining the comparative toxicity of 

 disinfectants of which the following is a brief summarized outline. 



Test Animals. The animals upon which the substance in question is 

 to be tested shall be white mice of not less than 15 nor more than 30 grams 

 weight. 



Dilutions and Dosage. The dose is to be calculated per gram of body 

 weight and should when diluted equal between 0.03 and 0.04 c.c. per gram 

 weight; that is, 0.6 to 0.8 c.c. for a 2o-gram mouse. The diluent is to be 

 distilled water and primary dilutions are to be made of such strength 

 that the dose is easily measured with a i c.c. pipette graduated into hun- 



