HOME ECONOMICS AND EDUCATION 661 



The germs of consumption, diphtheria, typhoid fever, plague, and in 

 fact the germs of all diseases yet discovered are killed by direct 

 sunlight in six to eight hours. Some die after a few minutes' ex- 

 posure. If germs are protected by blood, filth, etc., they are not 

 killed so quickly. 



Many disease germs are killed by the light which reaches them 

 in an ordinary room but this diffused light is not nearly so powerful 

 as direct sunlight and it usually requires several days to destroy 

 life. However, the important lesson is taught us that well-lighted 

 rooms do not harbor contagion. Good ventilation and light are im- 

 portant aids to any system of house or barn disinfection. 



Heat may be employed dry, as by baking in an oven, or moist, 

 as in boiling or steam. Dry heat is not as efficient as moist heat, 

 and has not as much penetrating power. Boiling destroys disease 

 germs as well as spores in from five to ten minutes. It is especially 

 useful for disinfecting clothing, bed-linens, handkerchiefs, cups, 

 plates, spoons, etc. Boiling water is also very useful for floors, walls, 

 and furniture. The addition of lye or strong soap helps its action 

 very much. 



Steam is the most efficient method of applying heat. It de- 

 stroys all forms of bacteria and spores very rapidly, and has great 

 ?ower of penetration. Steam under pressure is still more powerful, 

 t is apt to injure woolens and silk, and ruins leather, furs, and 

 rubber articles, like shoes and mackintoshes. Burning of course 

 destroys all infectious material, but the practical application of fire 

 is limited. 



Weil-Known Chemical Disinfectants. Bichloride of mercury, 

 mercuric chlorid, commonly known as corrosive sublimate, is one of 

 the most powerful germicides known. It is a deadly poison to man 

 and must therefore be used with the greatest care not only in the 

 house but in the barn. Many manufacturers make tablets of corro- 

 sive sublimate combined with chloride of ammonium, or common 

 salt, which are easily soluble and more efficient than the drug alone. 

 Directions are given for making a solution of any strength desired. 

 These can be bought at any drug store. Almost all germs which 

 do not have spores are killed in a half hour by a solution of 1 part 

 corrosive sublimate in 1,000 parts water. To kill spores a 1 in 500 

 solution must be used and one hour of 'time must be allowed. 



Bichlprid of mercury is a violent poison, and has the property 

 of combining with albuminoids to form inert compounds. It should 

 never be used to disinfect excreta, or substances containing blood or 

 serous fluids. Bichlorid solutions should not be kept in lead or tin 

 vessels, or poured through lead pipes, as the mercury combines with 

 these metals and injures them, besides affecting the germicidal effi- 

 ciency of the solution itself. 



The chief advantage in the use of bichlorid of mercury lies in its 

 great germicidal power when employed under proper conditions. 

 The disadvantages are its poisonous nature, its tendency to attack 

 certain metals, and the interference by albuminoids and other or- 

 ganic substances. Antidote. Egg whites and milk in abundance. 



