Abstract
A quantitative method was worked out for the registration of the stroke volume of the frog's heart under as nearly normal physiological conditions as possible, with the sole exception that oxygen was rigorously excluded. Carefully purified hydrogen was perfused continuously through the circulatory system, and through the bath which contained the heart, from which the stroke volume was recorded by the Asher recorder. As the pressure was observed in an arterial manometer, the work of the heart could be computed. The system contained venous and arterial valves. The pressure on the venous inflow-side, and the arterial resistance could be varied. The perfusing fluid introduced by Brömser, Barkan and Hahn was used.
In this system automatic beat could be observed for 61 hours, notwithstanding that for long periods the heart had been forced to beat more rapidly and do more work than normally. These observations demonstrate conclusively the possibility of the persistence of automatic excitations without oxygen for a much longer time than is stated in the current literature. If one could exclude the necrobiosis of the small fragments of tissue tied to the canula, the automatic beat would probably last longer.
The principal conditions for the persistence of a good automatic beat are the right composition of the circulating fluid, a periodical renewal of the bath fluid, low pressure on the venous side, an optimal arterial pressure, a constant perfusion of hydrogen, and especially the maintenance of circulation in case the beats begin to fail. Artificial beats of the heart, by a pump arrangement, restore the heart invariably.
The amount of work done by the heart and especially the question of fatigue and restoration was then examined. For over two days the anoxybiontic heart could maintain a fairly normal circulation. Perhaps of still greater importance is the fact that even restoration was possible, notwithstanding the lack of oxygen.
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