Heart Rate of the Developing Chick Embryo. ∗

Abstract

Summary

A new technique was used to measure the heart rate of developing chick embryos. Ballistocardiography should afford ideal conditions for observing embryonic heartbeats with a minimum of disturbance to the embryo. The same embryos can be measured on each day of incubation. The heart rate increased from day 4 through day 10 and then decreased until hatching time. The average frequency at 10 days was 280 bpm and 263 bpm at 19 days of incubation. Male embryos consistently had slower average heart rates than did females. No significant difference was observed in the average daily heart rate of embryos from 4 different genotypes, even though differences are apparent between adults of these genotypes. Mechanical disturbances or alterations in temperature had a marked effect on the heart rate of the embryo. Brief exposure to room temperature or slight injuries, such as those following insertion of electrodes, usually result in a decreased heart rate.