The American Journal of Physiology, 1919, Vol. 49 (Classic Reprint)

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Excerpt from American Journal of Physiology, Vol. 41 The results as published may be summarized as follows: The observations of Keith Lucas (1) that skeletal muscle, in simple contraction, responds in determinate, discontinuous gradients to relatively continuous change of stimulus intensity, have been verified (2), Like discontinuity has been found to obtain under continuous change of tetanic stimulation( 2). The unit, or minimal entity, of function has been found by direct observation to be, as Lucas inferred, the individual fiber (3). The most conspicuous sign of fatigue in the locally excited muscle is successive abrupt elimination of individual fiber activity through rise of threshold (2). Conversely, the staircase effect is in similar case dependent to an appreciable extent upon accession to complete function of previously inactive fibers, through progressive fall of threshold (2). The methods employed, heretofore only generally described, have naturally been subject to improvement and accretion in the progress of further work, and a stage is now reached where the technical results justify a more detailed account. With improvement in technique the graphic output has assumed an increasingly convincing character. The tracings reproduced, although introductory to a number of separate problems, are here presented as cumulative evidence of the independence on the part of individual contractile values toward change of stimulus or threshold. Part I. Methods For The Graphic Recording Of Fiber Movement Principles of Method The combined devices for recording are indicated essentially in the diagram, figure 1. The uncurarized preparation lies in a bath of Ringers fluid. Upon the bared muscle surface impinges one end of a bent glass tube lying in a vertical plane parallel with the fibers. The interior of the tube, filled with Ringer's fluid, is continuous with the bath containing the preparation by means only of a terminal pore of less diameter than a single fiber. The other end of this active liquid electrode is led into a separate bath of Ringers fluid in which is inamersed the porous cup of an unpolarizable terminal. A similar terminal system is immersed at a convenient point in the solution bathing the preparation. The circuit is completed through a coil subject to alteration of position with respect to an appropriately varied magnetic field (primary coil or moving magnet). About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.