File:Carpenter's principles of human physiology (1881) (14595042868).jpg

Identifier: carpentersprinci00carp (find matches)
Title: Carpenter's principles of human physiology
Year: 1881 (1880s)
Authors: Carpenter, William Benjamin, 1813-1885 Meneses, Henry Power
Subjects: Human physiology Physiology
Publisher: London : J. & A. Churchill
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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catedto and executed by the Muscles is immeasurable; but Helmholtz has shownthat if an electric spark, whose duration does not exceed one six- or seven-hundredth of a second, be allowed to strike a portion of fresh muscle, ameasurable period, amounting to 1 or 2-I00thsof a second, intervenes beforethe commencement of contraction. This he terms the period of latent con-traction or excitation. At the commencement of the contraction whichsucceeds, an instantaneous electrical discharge occurs, lasting less than the1000th of a second, and comparatively weak, but still probably equivalent tothat of the electric organ in fishes.^ The contraction which then takes place * See his successive Memoirs in Phil. Trans., for 1845, 1847, and 1850.t Tetanus, Leipzig, 1865.% See Bonders Essay on the Constituents of Food, translated by Dr. Moore, Dublin, 1866,p. 14, whore it is quoted as the observation of Meissner, and as corroborated by v. Bezold. 798 ON THE STRUCTURE AND FUNCTIONS OF MUSCULAR TISSUE.
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is not sudden and complete, but is divisible, according to Kliinder,* into fourstages, in the first of which the movement of contraction commences andslowly increases ; in the second there is great increase in the rapidity of thecontraction; the third is the period of maximum rapidity, and in the fourththere is a diminution of the rapidity. The first period can be much pro-tracted by heavy weighting, and the last period is very variable. Kliinder ( gives as the im- m duration of the latent excitationof fresh andlively muscle^ ijths of asecond, but whenexhausted andheavily weightedit rises to 1^Tr£hof a second; Diagram of a muscle curve as drawn on a travelling surface, a d e f the previous exten- line described by the point of the lever connected with the muscle; a, the base line. The vertical line, a c, marks the moment of stimulation; b, the beginning, Sion Oithemuscle d, the maximum, and e, the end of the contraction of the muscle. The interval j;m;nii;),pa *>. between a and b

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