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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 20-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- 



