Abstract: A heart beat cumulator records the number of heart beats occurring in each of a succession of ten minute intervals. An electrical signal of heart activity obtained from electrodes on the subject is amplified and applied to the input of a filter having a pass band of about 15Hz to 25Hz. The output of the filter is fed to a peak follower that provides a reference signal to a comparator which is actuated when the amplitude of the output of the filter exceeds the amplitude of the reference signal. Upon actuation of the comparator, the comparator emits a heart beat signal and triggers a monostable multivibrator that blocks the input to the comparator for about one third of a second. The heart beat signal is fed to a data counter.