480 STATE BOARD OF AGRICULTURE. 



the possibilities of the application of the fermenting capacity rather than 

 to exhaust the subject. 



One of the most interesting chapters, the influence of oxygen, cannot be 

 discussed because the few data obtained do not suffice for any conclusions. 

 It is the author's aim to present this paper more as a suggestion than 

 as a fact. It has been mentioned already that there is chance for im- 

 provement in the mathematical formula. Other criticisms might be 

 made on the interpretation of some doubtful points. But altogether, the 

 principal idea seems to be a valuable means to obtain information about 

 cell life which, without this method, can not be obtained. 



CONCLUSIONS. 



It is possible to compute the amount of acid formed by a single bacter- 

 ium cell in one hour, accurately enough to recognize decided changes in 

 the fermenting capacity. 



The computation requires nothing but the number of bacteria at the 

 beginning and the end of the experiment, the time of the experiment and 

 the acid formed in this time. All these data can be determined easily 

 by the customary laboratory methods. 



The amonnt of acid formed by one celP in one hour was found to be 

 in young milk cultures in the average of 57 determinations with various 

 strains, "^0.0,000,000,018 mg. or 18 X 10" mg. This is approximately the 

 Aveight of one single cell. 



There is no experiment on record to prove that in the first stage of de- 

 velopment the multiplication takes place without fermentation. As soon 

 as a determination of fermentation products is possible, it shows the 

 fermentation per cell to be the faster the younger the culture. 



There is a distinct difference in the fermenting capacity of different 

 strains. The weakest strain had an average fermenting capacity of 

 7.4 X 10'" while the strongest strain averaged 32.5 X 10" mg. per cell 

 and hour. 



The fermenting capacity decreases with the age of the culture, and 

 even if the acid is neutralized the fermenting capacity is loAver though 

 fermentation takes place again. Old cultures acidify slowly, even if 

 transferred into fresh milk, the rate of multiplication is also influenced 

 by long sojourn in the same culture. 



Peptone stimulates the acid formation of certain strains, but only by 

 increasing their numbers while the amounts of acid per cell remain un- 

 altered. Other strains show no material influence of peptone. In sugar- 

 free broth, they develop very slowly, but the fermenting cajiacity is nor- 

 mal if lactose is added. 



Temperature influences the fermenting capacity very decidedly. 



lAs counted by the plate method. 



