Day-Night Variations in the Cardiovascular System. Historical and Other Notes by an Outsider

Abstract

Among the earliest data-based documentations of diurnal variations in human physiological functions are those concerning heart rate and body temperature. In his famous textbook of 1801, Autenrieth states that “there occur within one minute in an adult human being in the morning 65 to 70, in the evening 75 to 80 pulsations” (my translation from German). In the same year, Gruner (1801) reported results from hourly measurements on two subjects; he found 65 pulses/min at 8 a.m, and 80 at 4 p.m. Similar observations had already been made by Reil (1796) who emphasizes that the acceleration of the pulse toward the evening does not occur in response to changes in conditions but is due to a “steady increase in irritability from morning to evening.” However, one has to remember that almost 100 years earlier John Floyer (1707–1710) published his monograph “The Physicians Pulse-Watch” which according to Albrecht von Haller (1788) “broke the ice” in the measurement of pulse rate, and in which exact numbers are given on pulse rate under various conditions such as food intake, exercise and sleep. In the introduction, Floyer mentions that initially he had made use of a sea minute-glass, “but because that was not portable, I caused a pulse watch to be made which run 60 seconds.” He approached Samuel Watson, Mathematician-inOrdinary to King Charles II and one of the masters of horology at that time, to construct for him a watch carrying a seconds hand. “There is no doubt about the identity of Samuel Watson as the maker of Floyer’s pulse watch” (Gibbs, 1971; for the only earlier watch with a seconds hand cf. Britten, 1911, and Kümmel, 1974).