j8 The Colorado Experiment Station 
the alkaline, the limits of growth being from —4° to +32° 
Fuller’s scale. The optimum reaction appears to be between + 1"> 
and +18. Growth is retarded by a neutral reaction, on the 
one side, and by +32 on the other, and is prevented entirely 
by —6 and +34. 
To tubes containing exactly 5 c.c. of sterile broth, sufficient 
standard NaOH or HC1 was added, with aseptic precautions, to 
give them reactions ranging from —40 to +40, each tube dif¬ 
fering by 2° from the others, thus: —40°. . . .—8°, —6°, —4°, 
—2°, 0°, +2°, +4°, +6°, +8°.+40°. Six tubes 
were prepared for each reaction, one of which was titrated to 
verify the degree of acidity or alkalinity. Without further 
sterilization, these tubes were inoculated with two loopfuls of 
a 48 hour broth culture and allowed to develop at 28° C. We 
found by trial that if the broth was sterilized after the acid 
or alkali had been added, the reaction might change consider¬ 
ably, especially in the case of the alkali, due, presumably, to 
certain chemical combinations which took place between the 
NaOH and the broth constituents at the sterilizing temperature 
(95.5° C. Altitude 4,981 feet above sea level). This was borne 
out by the fact that if the medium was not sterilized after 
adding the NaOH, —6° was sufficient to inhibit growth, but if 
sterilized, broth reacting —10° before being heated was required 
to accomplish the same result. 
Detailed results of the experiment are given in Tables Nos. 
3 and 4. 
table no. 3—relation to acid. 
Degree of Acid 
Growth Resulting After Given Number of Days 
1 d. 
2 d. 
3 d. 
4 d. 
5 d. 
6 d. 
7 d. 
8 d. 
9 d. 
10 d. 
0. 
_ 
— 
— 
+ 
+ 
+ 
+ 
+ 
o 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
4 . 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
6 . 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
8. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
10 . 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
12. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
14. 
(+) 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
16. 
( + ) 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
18. 
(+) 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
20_ _ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
22. 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
24. 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
26. 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
28 . 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
30 . 
— 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
32 . 
— 
— 
— 
— 
+ 
+ 
+ 
+ 
36. 
— 
— 
— 
— 
— 
— 
_ 
_ 
_ 
38 . 
— 
— 
— 
— 
— 
— 
— 
— 
— 
