PARAMECIUM INFUSION HISTORIES

I. HYDROGEN ION CHANGES IN HAY AND HAY-FLOUR INFUSIONS

¹ DEPARTMENT OF ZOÖLOGY, UNIVERSITY OF PITTSBURGH

A study of forty-seven Paramecium multimicronucleatum cultures made by boiling varying combinations of timothy hay and wheat flour in distilled water and seeding with 200 pure line Paramecia on the second day has yielded the following data:

(a) Cultures experienced a changing pH cycle which was invariably quite similar to that shown in Plate 1, if the Paramecia lived.

(b) The most successful timothy hay-flour medium was made by boiling one gram of hay and one tenth of one gram of flour in 700 cc. of water for ten minutes.

(c) Paramecia were observed to live in culture media whose pH ranged from 4.83 to 8.31 after the solutions had been violently stirred.

(d) As cultures evaporated, the alkalinity increased after the first four days. A hydrogen ion concentration of 8.31 was observed in infusion 4 when 20 cc. remained of the original 700. This infusion had a population of 6000 Paramecia to the cc. at that time, or about twelve times the normal dense population.

(e) Infusions of 7 liters' volume passed through the same pH cycles, but these cycles were considerably retarded as compared with the 700 cc. infusions.

(f) The tendency of infusions to kill the Paramecium population was associated with a persistence of the extremely acid condition for a period of several days, as is shown by Plate 2. This prolonged acid condition developed in infusions which were made with too much flour, too much hay, or too much of both ingredients.

(g) The radically changing hydrogen ion concentrations which were recorded in successful Paramecium cultures were thought to be due at least in part to a changing cycle of bacteria. We plan to try to determine what bacteria are responsible for these changes; the maximum, minimum, and optimum pH for each bacterium, the stages of the infusion in which each bacterium is most numerous; and the pH conditions which the metabolism of each bacterium induces.

(h) The extreme concentrations of Paramecium which were obtained in cultures which were covered after becoming concentrated by evaporation, where populations of as many as 2000 per cc. were kept for ten days continuously, leads us to question whether excretory matter is as toxic to the organism as has been supposed. It seems probable that the excretory matter becomes broken down and reorganized by bacterial and chemical action before it becomes sufficiently concentrated to injure the animals. It may be possible that in such reactions will be found the explanation of the pH behavior which has been reported.