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170 ANTISEPTICS AND DISINFECTANTS. 
practical disinfection, therefore, it is important to know what disease 
germs form spores and what do not. The following are known to 
form spores: The bacillus of anthrax, the bacillus of tetanus, the 
bacillus of malignant cedema, the bacillus of symptomatic anthrax, 
the bacillus of foul brood (infectious disease of bees). The following, 
so far as is known, do not form spores: The pus cocci (Staphylo- 
coccus pyogenes albus, aureus, and citreus, and Streptococcus pyo- 
genes), the micrococcus of pneumonia, the bacillus of typhoid fever, 
the bacillus of glanders, the bacillus of diphtheria, the spirillum of 
cholera, the spirillum of relapsing fever. 
Many agents which kill the growing bacteria are incapable of 
destroying the vitality of spores, and others only do so in much 
stronger solutions or after a long exposure to their action. 
(c) The number of bacteria to be destroyed, This is an essen- 
tial factor which has often been overlooked by those making experi- 
ments. To destroy the bacteria carried over to five cubic centimetres 
of distilled water by means of a platinum loop, is a very different 
matter from destroying the immensely greater number in five cubic 
centimetres of a recent bouillon culture. 
(d) The nature and quantity of associated material. The 
oxidizing disinfectants, like permanganate of potash and chloride of 
lime, not only act upon the bacteria, destroying them by oxidation, 
but upon all organic matter with which they come in contact, and at 
the same time the disinfecting agent is destroyed in the chemical 
reaction, which is a quantitative one. The presence, therefore, of 
organic material in association with the bacteria is an important 
factor, and if this is in excess the disinfectant may be neutralized 
before the living bacteria are destroyed. Other substances which 
precipitate the disinfecting agent in an insoluble form, or decompose 
it, must of course have the same effect. Thus the presence of sodium 
chloride in a culture medium would be an important circumstance if 
nitrate of silver was the agent being tested, as the insoluble chloride 
would be precipitated. And in the case of mercuric chloride and 
certain other metallic salts the presence of albumin very materially 
influences the result. Van Ermengem states that the cholera spiril- 
lum in bouillon is destroyed in half an hour by mercuric chloride in 
the proportion of 1: 60,000, while in blood serum 1:800 was required 
to destroy it in the same time. 
(e) The time of exposure is also an important factor. Some 
agents act very promptly, while others require a considerable time to 
effect the destruction of bacteria exposed to their action. Thus a 
solution of chloride of lime containing 0.12 per cent destroys the 
typhoid bacillus and the cholera spirillam in five minutes, and 
the anthrax bacillus in one minute (Nissen). On the other hand, 
