DISINFECTANTS. ANTISEPTICS 173 



media which has been previously impregnated with the drug under 

 examination. If the bacteria fail to develop characteristic col- 

 onies upon the media (gelatin, bouillon, etc.), then it is to be 

 assumed that the presence of the drug has prevented the growth of 

 the organisms. However, it cannot be concluded from the experi- 

 ment that the vitality of the organisms is destroyed. This fact is 

 only established when a pathogenic organism which has been thus 

 treated is inoculated into a suitable experimental animal and no 

 infection is produced. Only in the latter case can antiseptic proper- 

 ties be attributed to the drug. Non-pathogenic bacteria are 

 tested by permitting them to dry upon silk threads and placing 

 the threads in a solution of the substance under test. After a 

 time the threads are removed from the solution, washed in water, 

 and placed upon suitable culture media. If the substance being 

 tested actually possesses antiseptic properties no growth will occur. 

 Relative Rank of the Disinfectants. — In the beginning, the 

 individual disinfectants were tested bacteriologically in an en- 

 deavor to discover a drug which would destroy all known bacteria 

 when greatly diluted, but it was found that there is no such uni- 

 versal disinfectant. On the contrary, it was observed that specific 

 antiseptics are required to destroy individual species of bacteria, 

 just as certain antipyretics are required for the different types of 

 fever. For instance, corrosive sublimate is the most powerful 

 disinfectant for the virus of anthrax, but has only a very weak 

 action on tubercle bacilli and is much less effective than other 

 drugs (creolin, lysol, alcohol, formaldehyde) for superficial dis- 

 infection of the skin. Carbolic acid is relatively ineffective against 

 the tetanus bacillus, rabies virus, anthrax spores and tubercle 

 bacilH. Therefore, in disinfection the different drugs and bac- 

 teria must to a certain extent be considered individually. In a 

 general way, it can only be said that in the case of those micro- 

 organisms which exist in two different forms, namely, the con- 

 tinuous (spore) and vegetative (bacillus), the spores require much 

 more powerful antiseptics than the bacilli. Here, again, the 

 individual species of spores and bacilli show considerable differ- 

 ences in their ability to resist the action of the same drug. It is, 



