BIOLOGICAL EFFECTS OF HEAVY WATER

¹ FROM THE PHYSIOLOGICAL LABORATORY, PRINCETON UNIVERSITY

Heavy water (85-95 per cent) has been found not to prevent the luminescence of dried Cypridina nor to affect the luminescence of a fresh water luminous bacterium but to diminish the luminescence of a marine form; to retard growth of luminous bacteria, sometimes allowing slow growth without luminescence; to kill a number of protozoa and rotifers, but not to kill bacteria and not to injure Euglena irreversibly; to affect Euglena equally in light and in the dark; to affect only slowly protoplasmic rotation of Elodea cells and to penetrate into Elodea cells. In view of the slow and often reversible effects of heavy water, its action may be likened to that of a generally unfavorable environment, leading to progressive changes in the cell. No more can be said at present than to suggest that these changes are the result of differential effects on the rate of biochemical reactions which ordinarily proceed at a certain definite rate in relation to each other.