82 ELEMENTS OF WATER BACTERIOLOGY. 



number of colon bacilli will be small, since there is good 

 evidence that the majority of intestinal bacteria die from 

 exposure in cold water. If derived from cereals or the 

 intestines of wild animals the number will be insignificant 

 except in the vicinity of great grain-fields or when the 

 water receives refuse from grist-mills, tanneries, dairies, 

 or lactic-acid factories. 



The first recognition of the necessity for a quantitative 

 estimation of colon bacilli in water we owe to Dr. Smith, 

 who in 1892 (Smith, 1893^ outlined a plan for such 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 exam- 

 ination would lead to the condemnation of many good 

 waters. Freudenreich (Freudenreich, 1895) at the same 

 time indicated the necessity for taking into account the 

 number of colon bacilli present. He recorded the isolation 

 of the organism from unpolluted wells, when as large a 

 quantity of water as 100 c.c. was used, and concluded that 

 it was entirely absent only from waters of great purity 

 and present in large numbers only in cases of high pollu- 

 tion. This author also quoted Miquel as having found 

 colon bacilli in almost every sample of drinking-water if 

 only a sufficient portion were taken for analysis, but gave 

 no reference. 



The practical results of the application of the colon 

 test from this standpoint have always proved most instruc- 

 tive. As originally outlined by Dr. Smith, it consisted in 

 the inoculation of a series of dextrose tubes with small 



