DETERMINATION OF ORGANISMS 



71 



in midsummer bacteria capable of growth at 37° are 

 more abundant in normal waters than in winter and 

 spring. 



Winslow and Phelps examined 86 samples from 

 springs, wells, brooks and pools during the winter 

 and spring months and found only 12 which showed 

 more than 25 bacteria per c.c. and only 3 which showed 

 more than 100 per c.c. on lactose-agar. On the other 

 hand, of 58 samples from corresponding sources 

 examined in summer, 16 contained more than 100 

 bacteria per c.c. A series of 20 pools, ponds, and brooks 

 at Mt. Desert, Me., which were entirely free from 

 human or animal pollution, were examined in the late 

 summer of 1906. Only 4 of the 20 samples gave 



20° AND 37° COUNTS OF RAW WATER AT WILMINGTON 

 FILTER PLANT 



(Whipple, 1913) 



1908. 



Month. 



January. . 

 February . 

 March ... 

 April . . . . , 



May 



June 



July 



August. . . 

 September, 

 October . . , 

 November. 

 December . 



Bacteria per c.c. 



Gelatin, 

 20°. 



4630 

 6830 

 8800 

 3170 

 2010 

 1640 



3150 

 3140 

 3400 

 S180 

 6850 

 4100 



Bile-agar, 

 37°. 



124 



350 

 149 

 119 

 241 

 432 

 451 

 644 



439 



78 



203 



Per 

 Cent 



Bacteria per c.c. 



Gelatin, 

 20°. 



3880 

 4800 

 4620 

 5080 

 3340 

 2350 

 2940 

 1430 

 2620 

 1380 

 1650 

 4150 



Bile-agar, 

 37°. 



94 

 260 



387 

 347 

 229 

 158 

 57 

 230 

 619 

 129 



97 

 194 



Per 

 Cent. 



2 



5 

 8 

 6 

 6 

 6 

 I 

 16 

 22 

 9 

 3 

 4 



