CHAPTER XIV. 



THE BACTERIOLOGY OF WATER AND MILK. 



Bacteria in water. Water in streams and wells receiv- 

 ing surface drainage contains a variable number of bacteria. 

 When water comes from great depths in the earth it usually is 

 bacteria free. Water in springs and streams in an uninhab- 

 ited country contains few bacteria while that in wells and 

 streams in thickly inhabited districts is often teeming with 

 microorganisms. A few species are said to live (multiply) in 

 pure spring water which seems to be their normal habitat. The 

 bacteria found in water may be divided arbitrarily according 

 to their source into three classes. 



1. Water bacteria. These include bacteria having their 

 normal habitat in water. 



2. Soil bacteria. These include the bacteria that are 

 washed into the water from the soil. 



3. Fecal bacteria. These include the bacteria that have 

 their normal habitat in the intestine and which gain access to 

 water from the excreta of man and beast. 



Each of these groups of bacteria is characterized by cer- 

 tain species. The "water bacteria" are of no pathogenic sig- 

 nificance. They will not multiply at the usual incubator tem- 

 perature. The "soil bacteria" contain a large number of 

 organisms which may be found, especially after heavy rains, 

 in stream and well water. The "fecal group" of bacteria is 

 characterized by B. coli and B. lactis aerogenes. In addition, 

 water may contain important pathogenic species such as Bact. 

 anthracis when animals that have died of that disease are left 

 near the banks of streams or have been thrown into them. 

 Frankland 1 enumerates about 225 species of bacteria that have 

 been isolated from water. 



Jordan 2 divided the bacteria isolated from surface water 



1 Frankland. Microorganisms in water. London, 1894. 



2 Jordan. The Jour, of Hygiene, Vol. Ill (1903) p. 1. 



