Abstract Analysis of iatrogenic electrical arrhythmias serves to validate the assumptions postulated through the study of clinical electrocardiograms. Other disorders of rhythm, without clinical counterpart, have also become apparent. The recently introduced demand pacemaker functions as a pacemaker that is artificial and automatic, yet not parasystolic. Ordinarily, premature beats discharge but do not significantly depress the pacemaker rhythm. Under specifically induced abnormal conditions, the rhythmical discharge of this unit can be depressed by electrical impulses originating in another instrument. In this sense the function of the demand pacemaker is identical to that of other natural centers of impulse formation. For instance, artifically induced Gaskell rhythm of development also seems to result from a gradual cessation of inhibition of automatism, as predicted by Pick and associates from the study of clinical arrhythmias. The analysis of artificial arrhythmias presented in this communication helps to clarify the clinical use of the demand pacemaker. This instrument has specific indications, and when properly used is a valuable adjunct in the treatment of intermittent A-V block.