178 Sterilization and Disinfection 



solution, or are dried with a sterile towel. Andrews makes special 

 mention of the fact that the instruments must be completely im- 

 mersed to prevent rusting. 



Disinfection of the Wound. — Cleansing solutions (normal salt 

 solution) and disinfecting solutions (such as i : io,opo to i : 1000 

 bichlorid of mercury) are only appHed to septic wounds. 



IV. The Disinfection of Sick-chambers, Dejecta, etc.— The 

 Air of the Sick-room. — It is impossible to sterilize or disinfect the 

 atmosphere of a room during its occupancy by the patient. It is 

 entirely useless to place beneath the bed or in the corner of a room 

 small receptacles filled with carboHc acid or chlorinated Ume. These 

 can serve no purpose for good, and may do harm by obscuring odors 

 emanating from harmful materials that should be removed from 

 the room. The practice is only comparable to the old faith in the 

 virtue of asafetida tied in a corner of the handkerchief as a preventive 

 of cholera and smallpox. 



DISINFECTANTS 



Before one is able to make. a scientific apphcation of any germicidal 

 substance it is necessary to become acquainted with its micro- 

 organism-destroying powers. This may seem at .first thought to 

 be a simple matter, but is, in reahty, one of great complexity and 

 difficulty, for the various micro-organisms show marked variations 

 of their powers of endurance; different stages in the development of 

 the micro-organisms show different degrees of resisting power, and 

 the conditions urtder which the germicide meets the micro-organism 

 effect marked variations in action. These factors make it necessary 

 to vary the process of disinfection according to the exact purpose 

 to be achieved. , 



Let two examples serve to illustrate these requirements: Bichlorid 

 of mercury is one of the most powetful, reliable, and generally useful 

 germicides, but the strength of its solutions must vary according 

 to the purpose for which they are intended. It kills cocci and non- 

 sporogenic bacilli in dilutions of i : 10,000 in from five minutes to 

 twenty-four hours, but to kill anthrax spores requires twenty-four 

 hours' immersion in i : 2000 solution. If albuminous substances are 

 present in the medium containing the micro-organisms they precipi- 

 tate the salt immediately, diminishing the strength of the solution 

 and so retarding or perhaps preventing the germicidal action. 

 Again, certain micro-organisms are defended from the action of de- 

 structive agents, and among them the germicides, through the pres- 

 ence of waxy matter in their substance. Such is the case with the 

 acid-fast organisms, and notably the tubercle bacillus. Antiformin, 

 a combination composed of equal parts of liquor sodse chlorinatse and 

 a 15 per cent, solution of caustic soda, immediately dissolves the 

 great majority of micro-organisms, but has no destructive action 

 upon the tubercle bacillus. 



