CHAP T E R X X \^ 



-Experiments illustrating precantions 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 spoi'c-contaiuing 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, foi'ty- 

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



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