THE VITAL PHENOMENA OF BACTERIA. 85 



dilution, attack aldehyde groups and whose 

 poisonous action upon protoplasts and bacteria 

 has been proved by Low, Marpmann, and H. 

 Buchner, are prussic or hydrocyanic acid 

 (HCN), diamid (N 2 H 4 ), hydroxylamine (NH 2 

 OH), phenyl-hydrazine (C 6 H 5 ) 'NH.NH 2 ) and 

 sulphuretted hydrogen (H 2 S). Similar bodies, 

 which even in great dilution attack amido 

 groups, and whose poisonous, or disinfecting 

 qualities, have been proved, are, according to 

 Low, Buchner, Kitasato and Weyl, nitrous 

 acid (N 2 O 3 ), free .cyanogen or dicyaiiogen 

 (C 2 N 2 ), formaldehyde (H. COM), acetaldehyde 

 (CH 3 COH) and benzaldehyde (C 6 H 5 .COH). 



Some poisons, as for example alcohol, may 

 be harmless in small quantities since they are 

 easily oxidized in the presence of oxygen, and 

 others, such as salicylic acid, indol and phenol, 

 may condense or unite with other bodies into 

 non-poisonous or slightly poisonous products. 



The connection which the reactivity of atom 

 groups has with their toxic properties is shown 

 also by the fact that bodies which, in a given 

 degree of concentration, exert no injurious 

 effect upon bacteria at .the room temperature 

 (about 15), do destroy bacteria when the tem- 

 perature is raised to 37, and still more cer- 

 tainly if it be raised to 50 60. (Henle, 

 Behring, Heiden and Hammer have ascer- 



