Carpenter's principles of human physiology . It is very interesting to remark that the phenomena of exhaustion arenot produced in the living body within moderate limits, indicating that repa-ration is constantly taking place. Ofall the muscles of the body, the heartalone in its ordinary contraction givesa tracing corresponding to that ob-tained from a voluntary muscle on theapplication of an electrical shock—thatis to say, the heart constitutes the onlyinstance where each contraction isdefinite and single, and it presents thesame characters in all animals. Inall other instances, what is termed
Carpenter's principles of human physiology . It is very interesting to remark that the phenomena of exhaustion arenot produced in the living body within moderate limits, indicating that repa-ration is constantly taking place. Ofall the muscles of the body, the heartalone in its ordinary contraction givesa tracing corresponding to that ob-tained from a voluntary muscle on theapplication of an electrical shock—thatis to say, the heart constitutes the onlyinstance where each contraction isdefinite and single, and it presents thesame characters in all animals. Inall other instances, what is termed amuscular contraction consists of aseries of shocks or impulses, as shown in Fig. 296, in which a tracing is shownsuch as may be obtained from a muscle caused to contract by a voluntary effort,or to which excitations at regular intervals are applied. Here the effects of thesuccessive shocks are in the first instance superadded to one another till a Fig. 296. : ffA AAM /vw \ 1 ? ] DIAPASON 1 00. MUSCULAR IRRITABILITY. 801 Fig. certain degree of contraction is obtained, which remains permanent with thatamount of stimulation. If the electrical or mechanical* excitations are madeto succeed each other more rapidly (Fig. 297), the successive shocks unitemore quickly and completely, and thetotal contraction is greater in , if the excitations are repeatedmore than a certain number of timesper second, varying with the animaland the state of the muscle, the severalshocks fuse completely into one another,and tetanus is produced in which novibration is perceptible (Fig. 298). Themuscles of different animals responddifferently to electrical excitation. Inthe case of the bird,| permanent con-traction or tetanus is not produceduntil more than 75 shocks are communi-cated in a second, whilst the muscles of a tortoise are tetanized with onlythree shocks per second. RanvierJ found considerable difference in thereaction of the white and red muscles of rabbits to induced
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectphysiology, bookyear1
