252 



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. 



3. The temperature at which the experiment is conducted, a 



Same rod immersed in broth after 

 exposure to disinfectant. 



Fig. 87. — Glass rod in test-tube, for 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 rod; h, 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 unfavorable. 



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 threads 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 washed 

 in clean, sterile water, transferred to fresh culture-media, and their 



