260 



Value of Antiseptics 



more slowly; those containing still more, very slowly, until at last 

 there comes a time when the growth is entirely checked. 



Sternberg points out that the following conditions, which must be 

 avoided, may modify the results of experiment: 



1. The composition of the nutrient media, with which the anti- 

 septic may be incompatible (as bichloride of mercury and albumin). 



2. The nature of the test-organism, no two organisms being ex- 

 actly alike in their susceptibility. 



~]s. The temperature at which the experiment is conducted, a 



\^0 



Same rod immersed in broth after 

 exposure to disinfectant. 



Fig. 83. — Glass rod in test-tube, tor use in testing disinfectants. Tube 

 6 in. by % in.; rod 9 in. by J^ in. Ring marked with diamond i in. from lower 

 end, to show upper limit of area on which the organisms are dried. After ex- 

 posure the rod is placed in a similar tube containing broth, to test development. 

 a, Cotton plug wrapped around glass ro4; b, broth; c, gummed label on handle 

 of rod for identification; d, ring marked by diamond; e, dried organisms. 



relatively greater amount of the antiseptic being necessary at tem- 

 peratures favorable to the organism than at temperatures un- 

 favorable. 



4. The presence of spores which are always more resistant than the 

 asporogenous forms. 



II. The Germicidal Value. — Koch's original method of determin- 

 ing this was to dry the micro-organisms upon sterile thjeads of linen 

 or silk, and then soak them for varying lengths of time in the germi- 

 cidal solution. After the bath in the reagent the threads were 



