. American journal of physiology. ated ventricle is due, not to me-chanical violence, but to some factorwhose influence is overcome by the treat-ment with the saline solution. An in-teresting fact was brought out by thisexperiment, although bearing upon quitea different problem from the one underconsideration. The rhythm of the entireapex with recording lever; heart, including the partially separatedF, glass rod to which apex apex, was, in one experiment, twenty-eight is attached at lower end bv a • ^ n-i 1 r r ii , ,, ^, ; , ^ per mmute. 1 he rhythm of the apex fell,thread 6. The whol
. American journal of physiology. ated ventricle is due, not to me-chanical violence, but to some factorwhose influence is overcome by the treat-ment with the saline solution. An in-teresting fact was brought out by thisexperiment, although bearing upon quitea different problem from the one underconsideration. The rhythm of the entireapex with recording lever; heart, including the partially separatedF, glass rod to which apex apex, was, in one experiment, twenty-eight is attached at lower end bv a • ^ n-i 1 r r ii , ,, ^, ; , ^ per mmute. 1 he rhythm of the apex fell,thread 6. The whole ar- | . -^ . ^ immediately upon isolation, to seven perminute, which rate was maintained forsome time. During the later stages ofthe experiment the rate gradually in-creased, although the original value was never regained. Thisexperiment indicates that a ventricle in which spontaneous contrac-tions have been artificially induced has a rhythm of its own, whichis quite independent of the normal rhythm of the heart as a FlGlRi-: I. — Diagram illustrat-ing the method of suspendinga whole heart with partiallyisolated apex strip. A, en-tire terrapin heart; B, isolated by cuts Cand C \ D, thread suspend-ing whole heart to sup-port ; E, thread connecting ranged to be immersed atpleasure in any desired solu-tion. Rhythmic Activity of the Heart-Muscle. 107 The Latent Period. In a preceding paragraph the idea was advanced that the isolatedventricular strip remains at a standstill for the reason that it is not,under the conditions of normal life, spontaneously rhythmic. It isthe purpose of this section to describe the various artificial conditionsunder which rhythmic contractions may occur. Sodium chloride solution. — The first method of inducing beats hasalready been mentioned. It consists of immersing the strip in cent sodium chloride solution. A strip in this solution exhibitsa period of standstill before the onset of activity. This latent perio
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