Activity of Toad Lymph Hearts

The pulsations of the posterior lymph hearts of the toad, Bufo arenarum Hensel, have been recorded 1 by the optical method in the following way: a small funnel was applied over the pulsating zone and connected by rubber tubing to a Frank's capsule covered with a very delicate membrane such as that used for heart sound recording. 2 The records obtained were of good amplitude especially if the skin covering the lymph hearts was previously removed. The characteristic irregularity of the recorded pulsations was found to be due almost exclusively to variations in the duration of diastole. Bi- and tri-geminal rhythms were sometimes observed. A very remarkable fact, which we have verified in more than 150 observations, is that the 2 posterior (left and right) lymph hearts have always the same frequency per unit of time. This occurs in spite of the arrhythmia of individual hearts, the absolute asynchronism between left and right hearts, and the varying frequencies observed at any temperature between 0° to 40°C. The variation of pressure within the lymph hearts has been also recorded by introducing a fine needle into the cavity and connecting it with the recording capsule as described. The curve of intracardiac lymph pressure shows a rise in pressure together with the beginning of contraction. The rise is first slow and then more rapid; the decline in pressure is not so steep as the rise. It is difficult to ascertain in which point of the curve systole ends. Measurements show that the average period between the first rise in the pressure curve and its return to the base line, lasts from 0.46 to 0.55 sec. (Fig. 1.) In about 150 normal toads kept in a humid atmosphere, the frequency of the lymph hearts was determined at different temperatures from 0° to 37°C. The frequency increases with the temperature. We noted an average of 15 beats per minute at 0° and 123 beats per minute at 37°C. At room temperature (19°C) the mean frequency was observed to be 50 beats per minute. The increase in frequency follows the Van't Hoff law between 0° and 20°C.