Developing techniques to measure minute motions of the eggshell attributable to cardiac contractions of the embryo, we attempted to assemble techniques for simultaneous acquisition of ballistocardiogram (BCG), electrocardiogram (ECG) and arterial blood pressure. The procedure for implanting electrodes and catheter fulfilled requirements for the gas exchange through the eggshell to be maintained adequate. Despite of these appendages in the egg, the ballistic throw of the embryo could be detected from the eggshell employing the audio cartridge. The cartridge comprises a small magnet installed on a cantilever and moving in a core. The motion of the magnet in the core changes density of magnetic flux and produces electrical output proportionate to a velocity of its motion. Simultaneous recordings of BCG from multiple sites on the eggshell show that the amplitude of BCG waves is dependent upon a site of detection and the BCG is directional wave. Isochronal comparison between ECG, BCG and blood pressure indicates that the ballistic throw of the embryo body is caused by not only the ventricular contraction, but also atrial excitation; that is, the BCG comprises basic throws occurring during ventricular presystolic, isometric and ejection periods. Patterns of BCG waves which are composed of these basic throws are various among eggs and even in the same egg when its heart rate is altered with ambient temperature. The isometric contraction period remains constant irrespective of the heart rate, which is about 60 msec.
Simultaneous acquisition of electrocardiogram, ballistocardiogram and arterial blood pressure of chicken eggs.
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