II. Experimental results relating to the rhythmical and excitatory motions of the ventricle of the heart of the frog, and of the electrical phenomena which accompany them

Abstract

The results which are shortly stated in the following paragraphs relate to (1) the order and duration of the rhythmical and excitatory motions of the heart of the frog; (2) the normal electrical condition of the surface of the heart and the influence thereon of mechanical, chemical, and thermal injuries; and (3) the characters of the normal and of the excitatory electrical variation, and the modifications of those characters which are induced by injuries of the surface, and under the temporary influence of radiant heat. Section I.— Order and Duration of the Motions of the Heart . 1. Duration of the Ventricular Systole .—In the rhythmically contracting excised heart, i. e ., in the heart removed by cutting across the sinus, which will in this paper be called “the entire heart,” the frequency of the contractions is usually, in winter frogs, a little over 30 per minute. The systole of the ventricle lasts about one second. The contraction attains its maximum in a little more than half a second after its commencement, declining at first gradually, afterwards more suddenly. The sadden relaxation occurs between 0".7 and 0".9 after the commencement. At the close of this period the ventricle does not become entirely flaccid, for a lever resting upon it continues to descend for about a third of a second.