It has been previously shown that the respiratory and luminescent processes of bacteria are reversibly narcotizable (Harvey, '15, and Taylor, '34) and that the effect of narcotics on these two processes is a function of the concentration of narcotic. In general low concentrations of narcotic stimulate, higher concentrations produce a reversible narcosis, while still higher concentrations cause irreversible changes in both respiration and luminescence (compare Lillie, '16).
To determine more specifically the relation between narcotic concentration and narcotic effect experiments were performed in which the effect of ethyl urethane ('urethane,' ethyl carbamate) (0.05 to 0.75 molar) on marine luminous bacteria (B. fischeri, Beyerinck) was studied, in the hope that such information would throw further light on the mechanism involved in cell narcosis. The effect of the narcotic on both respiration and luminescence was measured. These two processes are known to be independent of each other and to have different thresholds of susceptibility to narcotic (Taylor, '34). In fact luminescence can be diminished 90 per cent in this form by narcotics without any diminution of respiration.
Luminous intensities were measured on a photometer bench and the rate of oxygen consumption was measured with a Warburg respirometer at 25" -h 0.01"C. Readings I National Research Fellow in Biology.
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