58 INFECTIOUS AND PARASITIC DISEASES. 



Most of the disinfectants are also deodorants, but the 

 reverse, it is to be remembered, is not true. Thus for- 

 mahn and carboHc acid are both deodorant and disin- 

 fecting substances, whereas musk, a deodorant, has no 

 disinfecting power. Bichloride of mercury, a most 

 powerful disinfectant, is only a deodorant if it is allowed 

 to act for a long period, for which reason it cannot be 

 used for this purpose in the sick-room. All of the dis- 

 infectants, when diluted, are also antiseptics. This 

 is important, in as much as in the strengths that many 

 of them are disinfectants, they are injurious to the 

 tissues of the body. Bichloride of mercury 1-50,000 

 is an efficient antiseptic, yet a strength of i-iooo is 

 required to kill all bacteria and their spores. The 

 same is true of formalin, which is antiseptic in a solution 

 of 1-50,000, germicidal only in a strength of 3 to 5 

 per cent. Substances like boracic acid, iodoform, etc., 

 on the other hand, are purely antiseptic, even when 

 employed in concentrated form. Strong solutions of 

 sugar and salt, as used for domestic purposes to pre- 

 serve various edibles from spoiling, are antiseptic but 

 not germicidal. 



The prominent place occupied by insects 



InSECTI- . r 1' 1 • . . 



as carriers of disease has given rise to a 



CIDES. . . ^ . , 



new interest in substances that will kill 

 them. Interest centers chiefly in the discovery of an 

 efficient substance that will be non-poisonous, yet 

 generally applicable. A substance combining both of 



