. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative. 198 COMPARATIVE PHYSIOLOaY. the whole heing very suggestive of a galvanic battery) closely resembles a muscle-nerve preparation or its equivalent in the normal body. The electric organs experience fatigue ; have a latent period ; their dis- charge is tetanic (interrupted); is excited by mechanical, ther- mal, or electrical stimuli ; and the effectiveness of the organs is heightened by elevation of temperature, and the reverse by cooling, etc. MUSCULAR WORK. If d
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative. 198 COMPARATIVE PHYSIOLOaY. the whole heing very suggestive of a galvanic battery) closely resembles a muscle-nerve preparation or its equivalent in the normal body. The electric organs experience fatigue ; have a latent period ; their dis- charge is tetanic (interrupted); is excited by mechanical, ther- mal, or electrical stimuli ; and the effectiveness of the organs is heightened by elevation of temperature, and the reverse by cooling, etc. MUSCULAR WORK. If during a given period one of two persons raises a weight through the same height but twice as frequent- ly as the other, it is plain that he does twice the work ; from such a case we may deduce the rule for calculating work, viz., to multiply the weight and height together. The effectiveness of a given muscle must, of course, depend on the degree to which it shortens, which is from one half to three fifths of its length; and the number of fibers it contains —i. e., upon its length and the area of its cross-section, taking into account in connection with the first factor the arrangement of the fibers; those muscles in which the fibers run longitudinal- ly being capable of the greatest total shortening. There is, as shown by actual experimental trial, a relation between the work done and the load to be lifted. With double the weight the contraction may be as great as at first, or even greater ; but a limit is soon reached beyond which contraction is impossible. This principle may be stated thus: The contrac- tion is a function of the stimulus, and is illustrated by the diagram below (Fig. 183). It has been shown experimentally that the chemical inter- changes in a muscle, acting against a considerable resistance,. Pig. 182.—The electi'ic-fieh torpedo, dissect- ed to show electric apparatus (Huxley); d, branchiee; c, brain; e, electric organ; g, cranium; me, spinal cord; n, ner
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