174 PATHOGENIC BACTERIA. 



that has been shown by competent experiments to fill the 

 requirements. 



It is not always necessary to use an expensive appa- 

 ratus in order to disinfect with formaldehyde; one can, 

 under forced conditions, hang up in the room a number 

 of sheets saturated with the 40 per cent, formaldehyde 

 solution. Of course, the number of sheets must be in- 

 creased for a large room. Care must also be exercised 

 that the hands do not become wet with the concentrated 

 formaldehyde solution. 



The "formalin," or 40 per cent, solution of the gas, 

 when fresh and tightly corked, is fatal to most bacteria in 

 dilutions of from 1 : 5000 to 1 : 25,000. It can be employed 

 with great advantage to spray the walls and floors of 

 rooms. It cannot be employed upon the skin or mucous 

 membranes, because of its marked irritating effect. 



The disinfection of the skin, both the hands of the 

 surgeon and the part about to be incised, is a matter of 

 importance. It is almost impossible to secure absolute 

 sterility of the hands, so deeply do the skin-cocci pene- 

 trate between the layers of the scarf-skin. The method at 

 present generally employed, and recommended by Welch 

 and Hunter Robb, is as follows : The nails must be 

 trimmed short and perfectly cleansed. The hands are 

 washed thoroughly for ten minutes in water of as high a 

 temperature as can comfortably be borne, soap and a brush 

 previously sterilized being freely used, and afterward the 

 excess of soap washed off in clean hot water. The hands 

 are then immersed for from one to two minutes in a 

 warm saturated solution of permanganate of potassium, 

 then in a warm saturated solution of oxalic acid, until 

 complete decolorization of the permanganate occurs, after 

 which they are washed free from the acid in clean warm 

 water or salt-solution. Finally, they are soaked for two 

 minutes in a 1 : 500 solution of bichlorid of mercury, 

 after which they are ready for use. 



Lockwood, 1 of St. Bartholomew's Hospital, recommends 



1 Brit. Med. Jour., July II, 1896. 



