DISINFECTION. 399 



disinfection is questionable. Bacteriologists are very doubtful 

 whether formaldehyde gas when so used is sufficient to insure 

 the thorough disinfection of a room. 



Many other chemicals have been used for disinfection, but 

 those mentioned are in the widest use and the most practical 

 from their cheapness and ease of application. 



APPLICATION OF DISINFECTANTS. 



In the study of the practical application of disinfectants 

 there are two points to be determined : (i) Where the disin- 

 fectant should be applied; (2) the proper disinfectant to be 

 used. 



i. The determination of the places where the disinfectant 

 should be applied is the most important factor connected with 

 the whole subject. Unless the disinfection is applied at the 

 proper place, there is likely to be a vast amount of misdirected 

 effort. If, for example, a dairyman is troubled with slimy milk 

 due to bacteria in the water in which he sets his cans, and in 

 attempting to get rid of it fails to notice this source of trouble, 

 he is likely to spend a large amount of money and labor in 

 disinfecting stalls and dairy, and possibly cows, without 

 producing any result ; while a little labor properly directed 

 toward the dairy water supply, would produce a satisfactory 

 result with far less trouble. The same thing will apply every- 

 where. A small amount of effort properly directed will be 

 successful, whereas a large expenditure of effort misdirected 

 will be useless. To determine the place where disinfectants 

 should be applied is the most difficult problem in disinfection. 

 No general rules can be given as a guide, but each case must 

 be determined by the intelligence of the individual who 

 attempts disinfection. It is, of course, impossible to state 

 the source of infection in many instances which may come 

 up for treatment. Although no general rules that can be 

 given, there is one fact which every one who attempts any 



