CHEMICAL STERILIZATION AND DISINFECTION. 85 



disinfected by thoroughly mixing them with two or 

 three times their volume of boiling water, after which 

 they are kept covered until cool. 



Sputum in which tubercle bacilli are present, as well 

 as the vessel containing it, must be boiled in 2 per cent, 

 soda solution for fifteen minutes, or steamed in the ster- 

 ilizer for at least half an hour. 



On the whole, in the laboratory we should rely more 

 upon the destructive properties of heat than upon those 

 of chemical agents. 



From what has been said, the absurdity of sprink- 

 ling here and there a little carbolic acid, or of placing 

 vessels of carbolic acid about apartments in which in- 

 fectious diseases are in progress, must be plain. Treat- 

 ment of water-closets and cesspools by allowing now 

 and then a few cubic centimetres of some so-called 

 disinfectant to trickle through the pipes is ridiculous. 

 A disinfectant must be applied to the bacteria, and must 

 be in contact ivith 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 greatest value in 

 the laboratory for the purpose of rendering infectious 

 materials harmless are : lieat, either by burning, by 

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

 ing in a 2 per cent, sodium carbonate solution for fifteen 

 minutes ; 3 to 4 per cent, solution of commercial car- 

 bolic acid ; milk of lime, and a solution of chlorinated 

 lime ("chloride of lime") containing not less than 0.26 

 per cent, of free chlorine. The chloride of lime from 



