BIOLOGY. 251 



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6. Chloride of Iron is applicable in exactly the same manner as 

 chloride of zinc, and is only suited for the disinfection of the dis- 

 charges from the body. It should have a specific gravity of 1,470, 

 and should contain about 40 per cent, of metallic chloride. 



7. Permanganate of Potash is only suited for the disinfection of 

 drinking-water; for" not being a volatile disinfectant, and being 

 very slow in its action and requiring much of it for any practical 

 purpose, it is not available as a common disinfectant; besides 

 which it attacks all kinds of organic matter, and will therefore 

 destroy clothing and be neutralized by every species of organic 

 substance. As a disinfectant of water, however, in localities 

 where good filters of animal charcoal cannot be obtained, it 

 may be usefully employed to disinfect water by adding it thereto 

 until the water retains a very pale but decidedly pink tint. The 

 permanganate which is sold generally has a specific gravity of 

 1,055, and contains about 6 per cent, of permanganate of potash. 

 It will take more than a pint of this liquid to disinfect a pint of the 

 rice-water discharge from a cholera patient, and even then the 

 disinfection is very uncertain. 



8. Animal Charcoal. I may state that, for the disinfection of 

 water and the removal of dangerous organic impurity, I have as- 

 certained by experiment that the best treatment is first to filter the 

 water through animal charcoal, and then to boil it .for a few min- 

 utes. It may then be safely drunk. 



The disinfection of bedding and all articles of clothing is best 

 effected by exposing them in an oven to a heat of from 260 to 300 

 Fahrenheit. The exposure should be sufficiently long to insure the 

 thorough heating of every part of the material to that temperature. 

 When such a process cannot be used, the clothing should be put 

 into boiling water, and kept there until the water cools to the com- 

 mon temperature. 



I refrain from entering into any explanation of the mode of 

 action of these several disinfectants ; for, whether the agent of 

 disease is a living germ, capable of reproducing itself in the human 

 body under certain conditions, as most likely it is, or whether 

 it is an unorganized, or, even as Dr. Richardson supposes, a crys- 

 talline compound, the practical results are the same, and are un- 

 questionable ; and, in conclusion, I would say, by way of sum- 

 mary, that for the disinfection of sick-rooms, chlorine and chloride 

 of lime are the best agents ; for the disinfection of drains, mid- 

 dens, and sewers, carbolate of lime and carbolic acid are the best ; 

 for the discharges from the body, carbolic acid, chloride of zinc, 

 or chloride of iron are the best ; for clothing, the best disinfectant 

 is heat, above 260, if a dry heat, and 212, if a wet heat ; and for 

 drinking-water, filtration through animal charcoal and a boiling 

 temperature. 



I may mention that the best disinfectant for stables and slaugh- 

 ter-houses is a mixed chloride and hypochlorite of zinc, and it has 

 the advantage of mixing freely with the liquid matters of the 

 slaughter-house, and not tainting the meat with any unpleasant 

 odors. We have used it very largely for this purpose, and it is 

 also applicable to the disinfection of houses in place of chloride of 



