The Intrinsic Rhythm of the Turtle's Heart Studied With a New Type of Chronograph, Together With the Effects of Some Drugs and Hormones

Abstract

It is well known, since the time of Ringer, that an excised heart, if properly supplied with oxygen in a physiological salt solution, will beat for several days, in fact until the tissue begins to disintegrate. Snyder 1 in connection with his studies on the effect of temperature on the heart beat of the Pacific terrapin (Chemmys marmorata) counted rates at intervals over periods of 11 hours and observed considerable changes in rate under fairly constant conditions. At 25°~1°C. the heart of the terrapin did not beat longer than 6 hours, due probably to the fact that this species is adapted to cold water.The question arises as to the constancy with which a heart can beat over a period of many hours or several days, if all external factors affecting rate are kept quite uniform. For this type of investigation some sort of continuous automatic recording mechanism is a necessity. The Loomis chronograph, a preliminary description of which has already been published, ~ is specially designed to record rates of periodically recurring processes.Anything which will actuate a relay will run the chronograph whose mechanism is essentially as follows:The time for ten pulsations to occur is recorded by the length of a line of ink drawn by a moving pen on a revolving sheet of paper. During the next four pulsa-1 Snyder, C. D., Univ.