General physiology; an outline of the science of life . essing the same high grade ofirritability. In order to cause contraction, by means of a mechanicalstimulus, in a frogs muscle, for example, a stronger shock to-the muscle-substance is needed than in the case of an infusorian. STIMULI AND THEIR ACTIONS 385 Every one who has been at the sea-shore upon a quiet summerevening has observed the production of light by mechanicalstimuli. The curious, transparent animal life that in quietweather exists at the surface of the water has the wonderfulpower, irrespective of the classes to which the anim
General physiology; an outline of the science of life . essing the same high grade ofirritability. In order to cause contraction, by means of a mechanicalstimulus, in a frogs muscle, for example, a stronger shock to-the muscle-substance is needed than in the case of an infusorian. STIMULI AND THEIR ACTIONS 385 Every one who has been at the sea-shore upon a quiet summerevening has observed the production of light by mechanicalstimuli. The curious, transparent animal life that in quietweather exists at the surface of the water has the wonderfulpower, irrespective of the classes to which the animals severallybelong, of glowing brilliantly at every movement of the boat orthe oars, or every dash of the waves. Where the water containsmuch plankton, such as Noctilucw, Radiolaria, eggs of Ctenophora,etc., the effect of a shower of sparks in the water can be producedas well indoors. Every time sea-water is stirred in a glass theunicellular organisms, at the moment of the touch with a glassrod, flash up brightly, and then immediately sink again into. Fig. 17.—Carchesium polypinum, a branched colony of A, Unstimulated ; B, stimu-lated by jarring. The single individuals jerk together by the contraction of the-myoids oftheir stalks. darkness. The experiment can be repeated innumerable times,and the spectacle that is presented is of wondrous beauty. Before leaving the excitation-effects of mechanical stimuli, onemore group deserves attention, viz., the results of rhythmicallyrepeated shocks. Phenomena that are produced only incompletelyby single shocks are expressed much more strongly by summation,providing that each succeeding impulse follows before the stimulusof the preceding one has passed away. This fact is demonstratedmost distinctly in contraction-movements, where one con-traction is superimposed upon another so that there is no timefor expansion to develop between them: a genuine crampthen appears, which is termed mechanical tetanus. Thepeculiarity of te
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Keywords: ., bookcentury1800, bookdecade1890, bookidgen, booksubjectphysiology
