444 STATE BOARD OF AGRICULTURE. 



in number. But it only seems impossible; by a mathematical calcula- 

 tion, the fermentini? capacity of the average single cell can be computed. 



The value of determining the fermenting capacity lies in the differ- 

 entiation of the two main microbial activities : multiplication and fer- 

 mentation. The amount of acid or alcohol or toxin formed by a cul- 

 ture is the result of many cells. We do not know the number that 

 entered into reaction, and even the counting of bacteria would not add 

 much to our knowledge since the number of cells is changing continu- 

 ously from the time of inoculation. For practical Avork, the distinction 

 between growth and fermentation per cell is not necessary, but for some 

 questions of physiological significance it is necessars'. For instance, it 

 has never been demonstrated whether the optimum temperature for 

 cell growth and the optimum temperature for fermentation are the 

 same. This question may even be of some practical value. It can be 

 decided only by determining the fermentation per cell, eliminating the 

 multiplication. In order to determine whether toxins or any other 

 compounds are direct or indirect products of metabolism, it remains to 

 be determined whether or not there is a direct parallelism between 

 growth and toxin formation. This can be done accurately by computing 

 the fermenting capacity. If a certain substance stimulates fermentation, 

 it is valuable to know whether this stimulation is due to an increased 

 number of cells, to a faster fermentation of each individual cell, or to an 

 increase in both fermenting and multiplying power. Many other simi- 

 lar problems could be mentioned where the fermenting capacity of the 

 single cell would be very helpful. 



The necessity of the distinction between fermentation and multiplica- 

 tion has alreadv been mentioned and demonstrated bv Duclaux (Traits 

 de Microbiologie, Tome 4, 1901, p. 328). 



"Imagine that we inoculate into equal portions of a medium equal 

 quantities of different lactic bacteria, all other conditions being exactly 

 alike. If we deteraiine, by some means or other, the amount of acid 

 produced in 24 or 48 hours, these results evidently would be taken as 

 a measure of the "activity" of different lactics under the same condi- 

 tions. It is well understood that the "activity" as defined above de- 

 pends upon the given conditions, and that the organisms under study 

 might range in different order, if one of these factors, e. g., the tempera- 

 ture, were changed. The activity, in the above sense, depends upon 

 the amount of inoculation, and although this is no specific character, 

 it must be known. 



However, very seldom is it determined. Usually, the practice of com- 

 parison has been to introduce into the flasks not the same quantity of 

 fully developed bacteria, but the same amount of inoculating material 

 which has to multiply first before beginning to act, thus the result is 

 a superposition of two factors which do not follow the same law: 1. 

 The power of multiplication. 2. The fermenting activity of the or- 

 ganism. In order to measure the activity alone, the multiplication has 

 to be nil or very insignificant. This can be accomplished, or nearly so, 

 by inoculating with about as many cells as are found in the same vol- 

 ume of rapidly fermenting liquid." 



"Activity" in the sense of Duclaux is the same as the suggested "fer- 

 menting capacity," only Duclaux uses as a basis the weight of bacteria, 

 and the present paper suggests the single cell as being simpler and more 

 easilv determined. 



