This and subsequent communications comprise a study of the factors which influence the biologic activity of radiation. The present paper deals with an explanation of the influence of the time factor on the response of tissue to measured quantities of radiation. The reaction medium has been the human skin in vivo, and the roentgen rays used were of low voltage and either unfiltered or slightly filtered.
The biologic response of living substances to measured quantities of roentgen rays and gamma rays is recognized by many as depending on the intensity rate. The accepted meaning of the term intensity rate implies the quantity of radiation delivered in a unit of time and is expressed as roentgens divided by the time in which they are applied, or roentgen per minute.
Probably the first published definite relation between biologic response and intensity rate was that of Holthusen in 1933.1 He gave a