46 Manual of Veterinary Microbiology. 



ranean waters. When these waters are used for hu- 

 man consumption an epidemic of typhoid fever may 

 result. The knowledge of this fact has enabled us in 

 numerous cases to trace the disease to its source and 

 check its extension. The bacillus of cholera is dis- 

 seminated in the same manner. 



Generally speaking, therefore, waters charged with 

 organic matters should be viewed with suspicion, and 

 it is necessary to take particular precautions in order 

 to avoid the pollution of alimentary waters by cess- 

 pools, dung-hills, trenches of liquid manure, by the 

 stagnant waters of the streets, etc. 



The vicinity of these reservoirs of organic detritus 

 to the sources of alimentary waters is always to be 

 dreaded, especially when the earth is little adapted to 

 filtration ; hence, it is preferable, especially in thickly 

 populated centers, to secure water which has filtered 

 through virgin soils and convey it to the cities by a 

 system of closed canals. 



Pathogenic bacteria preserve their virulence in 

 water for varying periods. It has been observed that 

 this virulence is preserved during four months for the 

 bacillus of charbon, one year for its spores; the bacillus 

 of typhoid fever retains its vitality for two months in 

 water, that of cholera for twenty-four hours in cess- 

 pools, and twenty-nine days in spring water; those of 

 glanders and tuberculosis for twenty and ten days re- 

 spectively (in water). 



Soil. — The germs of the soil are numerous, their 

 function being to transform organic matters of which 

 this medium is the great recipient ; but most of them 

 are without efiect on the organism of animals, Never- 

 theless, inoculation of vegetable mold into the small 



