File:An American text-book of physiology (1897) (14596696547).jpg

Identifier: americantextbook00howe (find matches)
Title: An American text-book of physiology
Year: 1897 (1890s)
Authors: Howell, William H. (William Henry), 1860-1945 Bowditch, H. P. (Henry Pickering), 1840-1911
Subjects: Physiology
Publisher: Philadelphia : Saunders
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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er temperature; g, h, contractionsat higher temperatures than 19° C, h being made when the temperature was 30° C.; i, k, I, show a differentseries of contractions, made as the temperature was increased from 30° C. toward the point at which themuscle-substance coagulates (after Gad and Heymans). (J) Effect of Drugs and Chemicals upon Jfuscular Contraction.—Certain drugsand chemicals have a marked effect upon the irritability and conductivity ofmu.scles, and these effects must nece.ssarily find expression in the amount of con-traction which would be excited by a given irritant. In addition to this, it isworthy of notice that the character of the contraction may be altered. The drug which has the rao.st striking effect upon the form of contraction isveratria. A few drops of a one per cent, solution of the acetate of veratria, in-jected beneath the skin of a frog whose brain has first been destroyed, in a fewminutes alters qompletely the character of the reflex movements; the muscles
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Fig. 57.—Myogram of muscle poisoned with veratria and that of a normal muscle; a, myogram from anormal gastrocnemius muscle of a frog—the waves at the close are due to the recoil of the recording lever;b, myogram from a gastrocnemius muscle poisoned with veratria, recorded at the same part of the drum. are still capable of rapidly contracting, but the contractions are cramp-like,the power to relax being greatly lessened. The poison acts upon the muscle-substance. If a muscle poi.soned with veratria be isolated and connected with^ Gad und Heymans: Archivfur Anatomic und Physiologic, 1890, p. 73. GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 129 a inyograpli, a contraction excited by a single induction shock will show a riseas rapid and as high as normal, but the fall of the curve will be greatly pro-longed (see Fig. 57). Often the crest of the curve will exhibit a notch, which shows that relaxa-tion may begin and be checked by a second contraction process which carriesthe curve up again

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