HYDROGEN ION CONCENTRATION OF PROTOZOAN CULTURES. JJ 



one of alkalinity, while in hay cultures there is a period of acidity 

 which lasts for a relatively long time in the life of the culture. 



Figure 2 shows graphically the relation between the titratable 

 acidity and hydrogen-ion concentration of a typical hay infusion 

 culture. A somewhat more gradual and noticeable change is 

 noted for titratable acidity than for hydrogen-ion concentration, 

 and this seems to show that a marked change in titratable 

 acidity is not necessarily accompanied by a correspondingly 

 marked change in hydrogen-ion concentration. 



Peters 1 and Fine 2 have shown that the acidity of hay infusions 

 is due almost entirely to bacteria, to carbon dioxide, and acid- 

 yielding hay constituents. This being the case, it is of interest 

 to see how in an ordinary hay infusion a piece of marble will 

 produce a fairly constant Ph. 



Figure 3 shows graphically the changes in Ph and in titratable 

 acidity and alkalinity in such a culture. These cultures gradually 

 become alkaline in reaction, as indicated by Ph, but still have an 

 appreciable titratable acidity. Cultures prepared in such a 

 manner ought to be useful for keeping organisms in media of 

 almost constant Ph. 



The above results on titratable acidity and alkalinity are 

 quite in agreement with those reported by Peters 1 and Fine, 2 

 and in addition show the relative changes in hydrogen-ion 

 concentration during the life of hay infusion and soil cultures. 

 The sequence of organisms and changes in hydrogen-ion con- 

 centration have not been particularly studied, but it is not 

 improbable that some relation between the two might be shown 

 to exist. 



1 Peters, A. W., 1907, Amer. Jour. Physiol., 17 and 18. 



2 Fine, M. S., 1912, Jour. Exp. Zool., 12, p. 265. 



