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Summary
• The actions of dilutions and potencies of copper sulphate on the growth of Chlorella were studied in order to determine whether a potency of copper sulphate was beneficial to a culture of Chlorella which had been poisoned by copper sulphate.
• The growth rate of Chlorella in Chu 10 culture medium was greatly reduced by a concentration of copper sulphate of 10−5 Molar (M). Algae grown in Moyse culture medium, which contain 3·2×10−7 M copper sulphate, were less sensitive to copper sulphate. Chlorella whose growth had been inhibited by copper sulphate was, when resuspended in fresh culture medium, more sensitive to further added copper sulphate than normal algae.
• Potencies of copper sulphate prepared in the laboratory, in the concentration range 4c (4×10−8 M) to 15c had no effect on the growth of either normal or poisoned algae.
• Several batches of a 15c potency prepared by A. Nelson & Co., Ltd. increased the rate of growth of both unpoisoned and poisoned algae. These results are attributed to the fact that the batches of potency contained a general growth stimulant, rather than to a stimulatory homœopathic action of the potency itself which would have affected the poisoned algae only.
