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Einthoven's String galvanometer-Electrocardiograph

One of the most singular objects the Museum preserves is the electrocardiograph based upon Einthoven’s string galvanometer. The Museum has two examples of this interesting scientific instrument, both manufactured at Établissements G. Boulitte, in Paris, between the 1910s and the first 1930s, and used in experimental physiology laboratories and shortly after in hospital pathology wards.

The incorporation of the electrocardiograph to everyday clinical practice along the 1930s was determinant to make cardiology become a medical specialty with its own entity. The road covered to that moment constitutes one of the most interesting chapters in contemporary history of science, starting mostly from the controversy around Galvani’s and Volta’s electric stimulation of muscles at the turn of the 19th Century. The development at that time of a new mechanicism-based medical science, where physiology was understood as the physics and chemistry of the animal organism, allowed a series of experiments and demonstrations which consolidated the so-called “laboratory medicine”. Thus, the need to measure the intensity and the variations of the electrical potential originated in muscles translated into the development of instruments able to plot the graphic registration of physiological functions. The construction of the galvanometer, the rheotom, the kymograph and the sphygmograph, and the experiments performed with them, established the basis for the clinical exploration of circulatory disorders. Circulatory physiopathologic semiology underwent a decisive expansion through the last third of the 19th Century, due in part to securing the first graphic registrations generated by the action currents of the cardiac muscle through the mercury capillary electrometer. Danish physiologist Willem Einthoven was able to solve stability problems and mathematical errors in graphic registrations, caused by the inertia of the electrometer through the developing of the string galvanometer in 1903.

This self-recording instrument allowed, through an electromagnetized quartz thread capable of being run through by an electrical current, securing steady electrocardiographical layouts. The physical and chemical theories were at that time combined with the existing knowledge on optics and photography. This way, it was possible to transform and project the movement of the quartz thread, through a voltaic arc lamp, to finally register the action on a mobile photographic film. The first set was modified and made accessible to French and English builders in the beginning of the 20th Century.

The new electrocardiograph allowed a better study of arrhythmias than that made through the polygraph, as well as a more accurate view of the ventricular hypertrophies. Medicine was opening then a new door, electrocardiography, whose technical basis has not yet altered, and destined to elucidate some of the mysteries of cardiac pathology.