Abstract
Disregarding sources of variation known to be present in the unselected data, it is shown that the frequency distribution of temperature characteristics (critical increments) calculated from all known series of observations, pertaining to a great variety of vital processes, exhibits a number of discrete modes. This eads to the view, already derived from evidence of a more specific sort, that such critical increments may be used to characterize definite processes in a controlling system of reactions which seem to be of widespread occurrence in living matter.