PHYSIOLOGICAL ONTOGENY : A. CHICKEN EMBRYOS. XIII. THE TEMPERATURE CHARACTERISTIC FOR THE CONTRACTION RATE OF THE WHOLE HEART.

The relation of heart rate frequencies to temperature in intact chicken embryos has been studied and the temperature characteristics calculated for each of a number of ages. These have been found to vary from 14,000 or better 12,000 micro for embryos 3 days old, to about 6,000 micro for others of 15 days. There appears to be a systematic change with time. If this inference is correct, important correlation with other properties of the pace-making function in the intact heart should become possible.