238 G. C. SupPpLEE, W. A. WHITING, AND P. A. Downs 
TABLE 2. Summary or Hiauest and Lowest Counts FounpD ON Eacu CoMBINATION 
OF INCUBATION TEMPERATURE AND MEpDIUM 
F Num- Num- | Num- | Num- | Num- 
eee Counts roe ber of | ber of | ber of | ber of | ber of aoa 
‘ as ti Seiad d Dee c counts | counts | counts | counts | counts wi 
Se een. Pree 2 up to up to up to up to up to 
temperate | ettont | nenes | 200° | 500. || 1000 | 5000) | arn ie ee 
: Pe Cerra Reon ae per cent | per cent | per cent | per cent | per cent 
Plaines jee 100.0 0 0 0 0 0 0 21 
Inactose often «4. ldbes 2 1 0 0 0 0 31 
Dextrose 37°. .| 444.9 10 6 4 2 1 il 10 
Plaines Ome: 519.1 17 11 1 1 1 1 2 
Lactose 30°...] 453.5 11 9 2 2 0 0 2 
Dextrose 30°. .| 778.6 D2; 17 11 4 2 0 1 
Plaime2 02ers. 411.4 12 3 2 0 ) 0 4 
Lactose 20°...| 498.5 5 3 3 1 0 0 4 
Dextrose 20°..| 664.8 21 13 6 3 1 0 5 
Motel N|pcerenn: 100 63 29 13 | 5 B £0 
* Twenty samples in which more than one combination of temperature and medium gave the lowest 
results are not included in this summary. 
The results given in table 1 may be compared in several ways to show 
the variation obtained from each medium and incubation temperature. 
The writers have preferred to make comparisons on the basis of the number 
of highest and lowest counts found under each condition and also to com- 
pare the average percentage variation in count of all samples, regarding the 
37° count on plain agar as 100 per cent. These comparisons are given in 
table 2, in which the outstanding features are as follows: (1) from all 
samples, higher counts were obtained from some other medium and tem- 
perature combination than the 37° count on plain agar; (2) of these higher 
counts, 63 per cent were increased twofold, 29 per cent fivefold, 13 per cent 
tenfold, 5 per cent fiftyfold, and 2 per cent more than a hundredfold. 
Comparing the effects of incubation temperatures on all media, it was 
found that 50 per cent of the highest counts were obtained at 30°, 38 per 
cent at 20°, and 12 per cent at 37°. Of the lowest counts recorded, 6.2 
per cent were obtained at 30°, 16.2 per cent at 20°, and 77.6 per cent at 
37°. 
