150 ELEMENTS OF WATER BACTERIOLOGY 



clear that the colon bacillus finds in the intestine of the 

 higher vertebrates an environment better suited to its 

 growth and multiplication than any other which occurs 

 in nature. Houston (1903^) records the number of B. 

 coli per gram of. normal hurnan faeces as between 

 100,000,000 and 1,000,000,000. It is almost certain 

 that the only way in which large numbers of these 

 organisms gain access to natural waters is by pollution 

 with the domestic, industrial, and agricultural wastes 

 of human hfe. If pollution has been recent, colon 

 bacilli will be found in comparative abundance. If 

 pollution has been remote the number of colon bacilli 

 will be small, since there is good evidence that the 

 majority of intestinal bacteria die out in water. If 

 derived from cereals or the intestines of wild animals, the 

 number will be insignificant except perhaps in the vicinity 

 of great grain-fields or where the water receives refuse 

 from grist-mills, tanneries, dairies, or lactic-acid factories. 

 The first recognition of the necessity for a quantita- 

 tive estimation of colon bacilli in water we owe to Dr. 

 Smith, who in 1892 (Smith, 1893*) outlined a plan for a 

 study to be made by the New York Board of Health on 

 the Mohawk and Hudson Rivers. Burri (Burri, 1895) 

 pointed out that the use of so large a sample as a liter 

 for examination would lead to the condemnation of 

 many good waters. Freudenrejich (Freudenreich, 1895) 

 at the same time indicated the necessity for taking into 

 account the numher of colon bacilli present. He recorded 

 the isolation of the organisms from unpolluted wells, 

 when as large a quantity of water as 100 c.c. was used, 

 ^d concluded that it was entirely absent only from 



