THE EFFECTS OF A LACK OF OXYGEN AND OF LOW OXYGEN TENSIONS ON PARAMECIUM

¹ From the Department of Physiology, Princeton University, Princeton, N. J., and the Department of Zoölogy, University of Bristol, England

1. Paramecium multimicronucleatum and P. caudatum were subjected to pure hydrogen, pure nitrogen, and known mixtures of hydrogen and oxygen, while in a thin hanging drop under microscopical observation.

2. In all cases there was a limited period of anaerobic survival, during which activity of swimming and of contractile vacuoles was gradually diminished. Finally the organisms stopped, blistered, and cytolysed.

3. Admission of sufficient oxygen, even after blistering had begun, gave recovery.

4. Survival under anoxic conditions was best in culture fluid maintained at a reasonable hydrogen ion concentration by the addition of small quantities of carbon dioxide to the hydrogen or nitrogen. Under these conditions some organisms survived as long as twelve hours.

5. Paramecium was extremely variable as regards the length of anaerobic survival in any one medium. This variability is ascribed to physiological condition and not to genetic factors.

6. Survival under anoxic conditions was much shorter in dilute phosphate buffer than in culture medium. This is tentatively ascribed to a lack of balance of ionic concentrations.

7. In phosphate buffer the rate of swimming was reduced at tensions of oxygen below 1 mm., and the organisms died within a short time at tensions below 0.2 mm. At tensions above 0.3 mm. some measure of recovery from lack of oxygen could be obtained.

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