Intracellular Electrogram of Embryonic Chick Heart

1. Electrograms of the exposed heart of chick embryo which was incubated for 54～96 hours, were recorded with the microelectrode technique. Embryo of 7 days' incubation and young chick 2 days after hatching served as the control. 2. The slow diastolic depolarization which has been accepted as the characteristic feature of the pacemaker cell in other vertebrate hearts, could ne recorded from the ventricle, atrium or sinus-area. Other features such as systolic depolarization were also observed in the present preparation. 3. The values of resting and action potential could not be measured precisely. It seemed likely that this unfavourable result was caused by the cell-injury around the insedted microelectrode-tip. 4. Certain characters of the action potential, such as the amplitude and the hump seen in the rising phase, were discussed from the view-points of intracellular as weell as extracellular recordings.