CHAPTER XXV. 



Experiments illustrating precautions to be taken in the study of 

 disinfectants and antiseptics Skin disinfection. 



INTO each of three tubes containing 10 c.c. one 

 of normal salt solution, another of bouillon, a third of 

 fluid blood-serum add as much of a culture of the 

 staphylococcus pyogenes aureus as can be held upon 

 the looped platinum needle. Mix this thoroughly, so 

 that no clumps exist, and then add exactly 10 c.c. of 

 1 : 500 solution of corrosive sublimate. Mix it thor- 

 oughly, and at the end of three minutes transfer a drop 

 from each tube into a tube of liquefied agar-agar, and 

 pour this into a Petri dish. Label each dish carefully 

 and place them in the incubator. Are the results the 

 same in all the plates? How are the differences to be 

 explained ? 



Into each of two tubes containing 10 c.c. the one of 

 normal salt solution, the other of bouillon add as much 

 of a spore-containing culture of anthrax bacilli as can 

 be held upon the loop of the platinum wire. Mix this 

 thoroughly so that no clumps exist and then add ex- 

 actly 10 c.c. of a 1:500 solution of corrosive subli- 

 mate. Mix thoroughly and at the end of five minutes 

 transfer a drop from each tube into a tube of liquefied 

 agar-agar. Pour this immediately into a Petri dish. 

 Label each dish carefully and place them in the incuba- 

 tor. Note the results at the end of twenty-four, forty- 

 eight, and seventy-two hours. How do you explain them ? 



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