66 BACTERIOLOGY. 



Sputum in which tubercle bacilli are present, as well 

 as the vessel containing it, must be boiled in soda solu- 

 tion for fifteen minutes or steamed in the sterilizer for 

 at least half an hour. 



On the whole, in the laboratory we should as yet 

 rely more upon the destructive properties of heat than 

 upon that of chemical agents. 



From what has been said, the absurdity of sprinkling 

 about, here and there, a little carbolic acid or in placing 

 about apartments in which infectious diseases are in 

 progress little vessels of carbolic acid, must be plain. 

 The disinfection of water-closets and cesspools by allow- 

 ing now and then a few cubic centimetres of some so- 

 called disinfectant to trickle through the pipes is absurd. 

 A disinfectant must be applied to the bacteria, and must 

 be in contact with them for a long enough time to insure 

 the destruction of their life. 



In the light of the latest experiments upon disin- 

 fectants, the place formerly occupied by many agents in 

 the list of substances employed for the purpose will most 

 likely be changed as they are studied more closely. 



The agents, then, which will prove of most value in 

 the laboratory for the purpose of rendering infectious 

 materials harmless are : Heat, either by burning, by 

 steaming for from half an hour to an hour, or by boil- 

 ing in a 2 per cent, soda solution for fifteen minutes ; a 

 solution of chlorinated lime (" chloride of lime "), in 

 which the percentage of chlorine is high ; 3 to 4 per 

 cent, solution of commercial carbolic acid ; and milk of 

 lime. The materials to be disinfected in either of the 

 lime solutions should remain in them for about two 

 hours. The solutions should be freshly prepared when 

 needed, as they rapidly decompose upon standing. 



