274. MORRIS S. FINE 
Fig. 1 ‘Phenolphthalein acidity’ for infusions of series A, B, and C; samples 
taken from top of media. Ordinates represent number of cubic centimeters of 
0.01 N NaOH per 100 ce. of infusion. Upper curves: series A, average acidity = 
; Maximum acidity = .---.----- ; minimum acidity = - ---- ‘ 
Middle curve: series B, average acidity. Lower curve: series C, average acidity. 
Curves for maximum and minimum acidity of series B and C are not given as the 
variations are not important. 
It would seem that for the ‘phenolphthalein acidity’ at least, 
the inconstant temperature was not an important consideration. 
Infusions of the entire series A (infusions started at different times 
and therefore experiencing different temperature changes) show 
no greater individual variations in acidity than does the group 
A-l . . . . A-6 (infusions started on the same day and 
hence subjected to the same changes in temperature). This is 
illustrated in table 2. For this reason, when calculating average 
curves, I have not considered it necessary to exclude infusions 
merely because they were subjected to different temperature 
variations. 
As to the factors underlying the production of acid, I agree with 
the view of Peters!® viz., that bacterial fermentation mainly is 
