Sensitization to Heat Due to Exposure to Light of Short Wave-lengths

This paper is a report of some experiments on the effect of heat upon organisms which have been exposed to fluorite rays. The experiments have yielded valuable information concerning the mechanism of the action of rays. They show that the exposed organisms (P.aramecium caudatum) are made extremely sensitive to the influence of heat. The experiments are of interest because they show the necessity of a careful control of the temperature of the radiated organisms both during and after the radiation. Heretofore investigators have paid but little, if any, attention to temperature control in their radiation experiments. They have, perhaps, considered the matter unimportant, since the rate of most photochemical reactions is independent of temperature. The effect of heat upon the organism which has been made sensitive to heat by radiation must be clearly distinguished from its effect upon the specific photochemical reaction, for in the former case the effect is upon a series of reactions initiated by the exposure and not upon the photochemical change itself. The heat sensitization resulting from radiation appears to be of general occurrence. I t has been found in Laminaria exposed to the rays from radium emanation 1 and in egg white exposed to the rays from a quartz mercury-vapor lamp. 2 In the case of the heatsensitized egg white visible coagulation occurs at a lower temperature than in the non-radiated control. The degree of sensitization increases with the amount of radiation so that with sufficient expo-