A Quantitative Description of the Short Term Changes in the Force of Contraction of Rabbit Papillary Muscle With the Pattern of Stimulation

Summary The peak isometric tension developed during a twitch of isolated rabbit papillary muscle has been measured. The rapid short‐term changes in the peak tension produced by changes in the rate of stimulation have been investigated in experiments designed to avoid the irreversible effects of anoxia and fatigue. The experimental results have been shown to be well described by a hypothetical system in which the peak isometric tension, F, developed in a twitch is directly proportional to the magnitude, just prior to the twitch. of a hypothetical quantity, P; thus, where K, a and b air constants and γ 0 is tht‐ value of γ at t = P declines suddenly in a twilch and is subsequently regenerated in way described by equation (2), where γ is another quantity which increases suddenly in a twitch by an amount Δγ, and declines in between twiches according to equation (3).