92 ATLAS OF BACTERIOLOGY. 



take, at the end of one minute, five minutes, ten 

 minutes, fifteen minutes, thirty minutes, one hour, 

 etc., a small platinum loop full of material, place the 

 latter in 10 c.c. of lukewarm liquefied gelatin, and form 

 plates. We then obtain statements like the following : 

 x per cent of the disinfectant proves fatal in twenty 

 minutes, y per cent in one minute, etc. If we sus- 

 pect that the trace of disinfectant, which is conveyed 

 by the loop, may have made the gelatin aseptic and 

 may thus have simulated destruction of the bacteria, 

 we should make a control inoculation of fresh material 

 in gelatin to which a similar trace of the disinfecting 

 fluid has been added. 



The disinfectant to be tested should always be dis- 

 solved in water. If, on account of the slight solubil- 

 ity in water, the use of alcohol in the production of 

 the original solution is indispensable, special control 

 experiments are necessary in order to show that the 

 action of the alcohol was not injurious. 



When using nutrient media which are rich in 

 albumin, we require much larger amounts of the 

 disinfectant, both for the production of asepsis as 

 well as for that of antisepsis, than when using media 

 which are poor in albumin.* Thus in bouillon 

 creolin produces asepsis when present in the propor- 

 tion of 1 : 15000-1 : 5000 ; in beef serum only in the 

 proportion of 1 : 150. In bouillon free from peptone 

 or containing one per cent peptone, cholera vibriones 

 are killed in one-half hour on the addition of 0.01 per 

 cent HC1 ; on the addition of two per cent peptone, 

 only when 0.04 per cent HC1 is added. For diag- 

 nostic purposes we will usually make the tests in one 

 * Phenol is said to be an exception. 



