THE VITAL CONDITIONS OF BACTERIA. 91 ' 



poison which will just produce asepsis, i.e., inhibi- 

 tion of development. 



For example, a ten-per-cent solution of the disin- 

 fectant is prepared, and 1, 0.5, 0.3, 0.1 c.c., etc., are 

 added to 10 c.c. of liquefied gelatin. The tubes then 

 contain 1 per cent, 0.5 per cent, 0.3" per cent, 0.1 

 per cent of the disinfectant; stick, streak, or plate 

 cultures are then made with the bacterium which is 

 to be tested. We may also inoculate with material 

 which contains only spores (material which has been 

 freed from all bacilli by heating for half an hour to 

 70 C.) in order to note whether these spores grow 

 into cultures. 



Behring makes this test in the following practical 

 form : From the fluid, infected nutrient medium (for 

 example, serum) which is to be tested a drop is 

 taken before the addition of the antiseptic, and, after 

 being placed on the lower surface of a cover-glass, is 

 enclosed, by means of some vaseline, in a hollowed 

 glass slide (vide Technical Appendix) . Then larger 

 and larger quantities of the disinfectant are added 

 gradually to the serum tube, and after each addition 

 a drop culture is again made. After remaining from 

 twenty-four to forty-eight hours in the incubator, 

 we can convince ourselves with the microscope of the 

 growth in the different drops. 



In case of a degree of concentration necessary to 

 antisepsis, the fungus is cultivated in bouillon and 

 10 c.c. of the bouillon (which is still free from spores 

 and which has been filtered through asbestos in order 

 to get rid of any clumps of bacilli which may be 

 present) are replaced with a corresponding amount 

 of the disinfectant solution. From these tubes we 



