The Heart Rate of the Developing Chick

Abstract

1. Records taken of the heart beat of the hen's egg during incubation, which were made without injury to the embryo, confirm the results obtained by Cohn. 2. The heart rate of the chick rises sharply during and immediately after hatching, but thereafter appears to remain nearly constant throughout life. 3. There is no obvious relation between the variations of the pulse rate and of the metabolic rate which are observed during the development of the hen. 4. No difference was found in the average heart frequencies of the two sexes, either during incubation or after hatching. 5. The newly hatched chick shows a remarkable accelerator action of the sympathetic. No evidence of vagal control has been found in the chick, but such control exists in the duckling. 6. Very slight alterations in temperature have a marked effect on the heart rate of the embryo and of the newly hatched chick.