MECHANICAL MEANS OF ASEPSIS 507 



our command. Dry heat, to be efficacious, must be applied at a tempera- 

 ture of 140° C. (284° F.) for three hours to kill all bacteria and spores; 

 but this degree of heat scorches most fabrics and destroys many materials. 

 Boiling water quickly kills all non-spore-bearing pathogenic bacteria, 

 and these include most of the organisms causing the common contagious 

 and infectious diseases (anthrax excepted). Two hours of continuous 

 boiling will not destroy the most resistant micro-organisms — the spores 

 of the hay bacillus — but moist or saturated steam, at 230° F., will infal- 

 libly kill any spores whatsoever within a few minutes. Fire is the most 

 complete disinfectant, because it not only destroys germs, but their food 

 and products. Water, like air, dilutes germs and aids oxidation and 

 destruction of organic matter ; but, again like air, drinking water may be ' 

 the source of infection when sufficiently contaminated. 



MECHANICAL MEANS OF PROCURING ASEPSIS. 



Hitherto the placing of sole reliance on chemical agents, to secure 

 surgical sterility of the skin and fresh infected wounds has been a mis- 

 take. It has been impossible to render living, infected tissue sterile by 

 merely bathing it in chemical solutions. In other words asepsis has been 

 procured most satisfactorily by mechanical means and the chemical has 

 played a secondary part. 



Thus the most efficient method has been to remove the hair from the 

 skin surrounding a wound or operative area, and to shield the wound with 

 sterile gauze meanwhile. Then the skin was actively scrubbed for 10 

 minutes with green soap and water and followed with 70 per cent, alco- 

 hol. The wound was then exposed, foreign matter and loose tissue 

 removed by forceps and scissors, and the wound scrubbed, syringed or 

 douched for 10 minutes with normal salt, lysol, or other solution. Now 

 we have learned we can sterilize the skin and infected raw tissue without 

 the scrubbing, and washing, and other laborious methods and with appar- 

 ently as good results by using iodine (See p. 613). 



CHEMICAL AGENTS. 



Mercuric bichloride, carbolic acid, quicklime, chlorinated lime, sul- 

 phurous acid, and chlorine, are more frequently employed as disinfectants. 

 Corrosive sublimate solutions are decomposed by keeping, and by contact 

 with albumin and ammonia. Acids, or common salt, added to bichloride 

 solutions prevent, in a measure, ■ this decomposition ; but, nevertheless, 

 mercuric bichloride is rendered unfit for the disinfection of masses of 

 decomposing albuminous matter, as manure. One of the best solutions, 

 employed by the Paris Disinfection Service, is composed of corrosive 

 sublimate 2 grams; tartaric acid, 4 grams; and water, 1 litre (1-500), 

 colored with 5 drops of a 5 per cent, solution of indigo carminate. An 

 English solution, in common use, consists of corrosive sublimate, 1 ounce ; 

 hydrochloric acid, 2 ounces, and water to make 3 gallons (1-768). The 

 usual strength of corrosive sublimate solutions, for disinfection, varies 

 from 1-500 to 1-1000. These solutions are suitable for articles made 

 wholly, or in part, of leather, rubber and fur; for blankets, cotton and 

 woolen fabrics, and for floors, walls, and wood work of stables. Surgical 



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