Increased susceptibility of protozoa to poison due to treatment with alcohol

The protozoa on which the experiments were performed were from two cultures (each comprising four lines)—one of Paramecium which had been under daily observations for over nine months, and the other of Stylonychia which had been under daily observation for over two months when the experiments were begun. The daily rate of division of each of these cultures was known.

From each of these cultures two secondary cultures were isolated line by line, and these were treated in identically the same way as the original or “control” cultures, except that each received daily for over a month a certain amount of alcohol in the culture medium of hay infusion. One culture received one part of alcohol to 2,500 parts of culture medium and the other received two parts of alcohol to 2,500 parts of culture medium.

Then, from each of the two control cultures and from each of the four alcohol treated cultures, other cultures were isolated and treated in identically the same way as the culture from which each was respectively derived, except that each received one part of copper sulphate to 1,250,000 parts of culture medium.

From these experiments it was found that whereas the average rate of division of the alcohol treated cultures was more rapid than that of the control, the alcohol treated cultures were more susceptible to copper sulphate than the control series, and finally (in the cultures carried to conclusion) died out while the control series treated with copper sulphate survived. It was found that the protozoa which were subjected to the greater strength of alcohol (2/2,500) divided more rapidly than those which were subjected to the less strength and also were more susceptible to the influence of copper sulphate.