SIMILE METHOD FOR CLASSIFICATION OF BACTERIA 17 



A clear area about the stroke averaging more than 2 mm. 

 in width classifies the diastatic action as strong, while a width 

 of 2 mm. or less marks it as feeble and the absence of a halo as 

 absent. These are the three terms used on the classification 

 card of the Society of American Bacteriologists. As the loopful 

 of growth from an agar slant is the unit amount of inoculation 

 which is used in all of the other tests which go to make up the 

 group number of an organism, the starch agar test is consistent 

 in this respect. 



As used in this laboratory, some of the evident advantages of 

 this method over the potato slant method are the decrease in 

 time and labor in the preparation of the media, and the greater 

 accuracy which the average worker can obtain. 



The starch agar gives best results if used before it is two 

 weeks old, as after that period of time the starch becomes changed 

 and spots of reddish purple develop on the addition of iodine 

 solution. 



As to the comparison of this method with the potato test, it 

 has been found that for the organisms of dairy products, ap- 

 proximately the same results are arrived at whether one test or 

 the other is used. 



