Microchemical Color Reactions as an Aid to the Identification and Classification of Brain Tumors.

fraction of the corresponding mean frequency. For the different individuals the amount of deviation is about the same. The critical termal increment, ,u, is in this case 12,200 calories. This agrees quantitatively with the increment for a number of other activities among arthropods' in which "nerve center" activity may be presumed to be the determining phenomenon. Our purpose now, however, is not to dwell upon the meaning of the specific increment for heart rhythm, but to present the fact that when sources of variation are reduced to a reasonable minimum the velocities of. biological phenomena are found to obey with exactitude the law of temperature influence upon irreversible chemical processes. The nature of the residual variations in velocity (frequently), as disclosed in this and other instances,2 makes it important for precise analysis to secure numerous observations at close intervals of temperature.5 Careful analysis of this type applied to representative cases makes it possible to interpret instances unavoidably involving more influential sources of variation. A detailed discussion of the experiments, and a comparative account of thermal control of heart rhythm in various animals, will appear in The Journal of General Physiology. Crozier, W. J., J. Gen. Physiol., 7 (123, 189); these PRocMEDINGs, 10 (461). 2 Crozier, W. J.,. and Federighi, H., J. Gen. Physiol., 7 (151); Crozier, W. J., and Pilz, G. F., Ibid. 6 (711). 3 We are glad to thank Mr. L. R. Campbell for his assistance in caring for the larvae. 4 Crozier, W. J., and Federighi, H., Proc. Soc. Exp. Biol. Med., 21 (56); J. Gen. Physiol., 7 (151); Glaser, O., Ibid.; J. Gen. Physiol., 7 (177). 6 The reasoning underlying the biological use of the Arrhenius equation for reaction velocities as function of temperature should warn against "averaging" observations from different individuals. Failure to avoid this practice has resulted in some curious errors in the literature of "temperature coefficients."