GERMICIDES, ANTISEPTICS, AND ANTISEPSIS 265 



Filtration. In the laboratory, and on a larger scale in the 

 management of water-works, filtration is a method of steril- 

 ization, acting as it does by mechanically separating bacteria 

 from a solution. 



General Measures for Disinfection. For discharges 

 urine, feces, sputum, vomitus solution of phenol, 5 per cent., 

 also fresh milk of lime, i part lime to 4 parts water. Lime 

 is of -value only when sufficient alkali present. Blankets, woolen 

 clothing, soiled handkerchiefs, linen, boiling in steam, for- 

 maldehyd gas, or hot-air exposure. 



Articles of little -value should be burned. Books can be sub- 

 jected to formaldehyd vapor or immersed in gasolene. 



The hands and body washed in strong soapsuds and then 

 in i : 1000 mercuric chlorid solution. 



Tincture of iodin, for the skin and hairy parts, painted 

 over the field of operation, has come into vogue as a very 

 efficient antiseptic. 



Woodwork and floors should be washed with soapsuds 

 and i : 1000 solution of mercuric chlorid, the room itself 

 subjected to formaldehyd vapor. 



Testing the Value of Disinfectants. Rideal-Walker 

 Standard. For comparing one disinfectant with another, 

 they are compared with phenol solutions of known strength 

 in their action on a culture of some microorganism (the 

 Bacillus typhosus is now used in most laboratories). A 

 standard temperature of 20 C. has been adopted by the 

 workers of the United States Hygienic Laboratory, and some 

 changes have been made by them in the Rideal-Walker 

 method, so that it is referred to as the "Hygienic Labor- 

 atory Phenol Coefficient." 



The medium is made of beef-extract, according to the 

 American Health Association standard, and must have a 

 reaction of +1.5 in test-tubes containing 10 c.c. each of the 

 medium. 



The organism is a twenty-four-hour-old filtered broth 

 culture of the Bacillus typhosus. Temperature of cultures 

 and dilutions must be brought up to 20 C. 



