The Significance of B. Coli in Water. 139 



from different sources by incubating measured samples 

 with equal amounts of nutrient broth and isolating upon 

 agar. In 45 samples of well-waters they found B. coli 

 7 times in .01 c.c, 9 times in .1 c.c, and 7 times in i c.c. 

 In the other 22 cases it could not be found in i c.c. and in 

 4 cases not in 100 c.c. One sample showed it only in 600 

 c.c. and i not in 750 c.c. Of 29 river-waters, only 2 failed 

 to give positive results in .1 c.c. and 14 showed B. coli in 

 .001 of a c.c. or less. In sewage the number varied from 

 I to 1,000,000 per c.c. The authors conclude that a 

 quantitative estimation of the B. coh content furnishes a 

 good measure of the fecal pollution of water. Some of 

 the best French bacteriologists have recently come to a 

 similar conclusion. Gauti6 (1905) holds that the quanti- 

 tative determination of B. coli is of the highest importance 

 in water analysis; and Vincent (1905), in an excellent 

 review of the subject, gives strong reasons for maintaining 

 the same position. He finds B.' coli absent from spring 

 and well-waters of good quality and present ia polluted 

 water in proportion to its pollution. A number of French 

 rivers showed numbers of B. coli varying from i to no 

 per c.c. He concludes finally that water containing B. 

 coH in .1 to i.o c.c. is tinfit to drink, while if the organism 

 is found in i.o to lo.o c.c. it is of doubtful quality. 



Altogether the evidence is quite conclusive that the 

 absence of B. coli demonstrates the harmlessness of a 

 water as far as bacteriology can prove it. That when 

 present, its numbers form a reasonably close index of 



