DETERMINATION OF ORGANISMS 



69 



per c.c. at 20 and 55 at 37 with an average of 7 red 

 colonies. 



BACTERIAL CONTENT OF 147 SHALLOW WELLS 



PERCENTAGE OF SAMPLES IN EACH GROUP 



Bacteria per c.c. 



Significance of High Temperature Counts. Important 

 data as to the distribution of bacteria which will develop 

 at high temperatures may be found in a paper by 

 Gage (1906), coupled with a suggestive discussion of the 

 general significance of bacterial ratios. The table on page 

 70 shows some of the most significant results obtained by 

 plating waters of various degrees of purity at 20, 40 and 

 50. We have rearranged the lines of the table so as to 

 make the progression from more to less polluted waters 

 a fairly regular one. The colony count at 50 shows an 

 even sharper differentiation than that at 40. Gage 

 rightly concludes that " the information to be obtained 

 by counts of bacteria and acid-producing organisms at 

 any one of the above temperatures is greatly increased 

 by the combination of the results obtained from counts 

 at two or more temperatures." 



