Theodor Wilhelm Engelmann

Abstract

Physiological ResearchEngelmann's research career began when he was 15 years old and a student at the Thomas School in Leipzig. He studied infusoria (ciliated protozoa), an interest that led to his study of bacteria at Utrecht. Using a microspectrophotometer, Engelmann identified the phenomena of chemotaxis and phototaxis, having observed that certain bacteria were attracted by higher oxygen concentrations. 2,5 Extending his interest in the electrophysiology of striated muscle to cardiac muscle, he introduced the terms "chronotropic" for heart rate, "inotropic" for contractility of the heart, and "dromotropic" for conduction velocity. 6 In an extensive series of experiments, he studied the effect of electrically induced extrasystoles on the cardiac rhythm in experimental animals. These experiments led to his contributions to the phenomena of the refractory period and the compensatory pause. 7 He devised the ladder diagram (laddergram) as a way to depict the successive contractions of the sinus, atrium, and ventricle and to analyze arrhythmias. 8 Myogenic Automaticity of the HeartOne of Engelmann's most significant contributions to cardiac physiology was his support for the hypothesis of the myogenic theory of the heartbeat. Drawing an analogy to the physiology of smooth muscle in the intestinal tract, the ureter, and the gallbladder, he postulated that the heart's automaticity was of myogenic origin. At the time, the prevailing theory was that the rhythmic nature of the heartbeat was neurogenic in origin, 9 but he disputed the notion that the excitation of the heart originates from the ganglia.