. Electro-physiology. Electrophysiology. ORGANISATION AND STRUCTURE OF MUSCLE that muscle-fibres exhibiting such fixed waves of contraction, when considered on a gypsum ground in the plus and minus condition, exhibit no particular alteration of colour in the con- tracted as compared with the relaxed parts, although normally increase of bulk in a muscle-layer does perceptibly deepen the colour, when two relaxed fibres partially cover each other. Even high waves of contraction exhibit, in comparison with the relaxed portions of the fibre, little or no alteration qua increase or decrease of
. Electro-physiology. Electrophysiology. ORGANISATION AND STRUCTURE OF MUSCLE that muscle-fibres exhibiting such fixed waves of contraction, when considered on a gypsum ground in the plus and minus condition, exhibit no particular alteration of colour in the con- tracted as compared with the relaxed parts, although normally increase of bulk in a muscle-layer does perceptibly deepen the colour, when two relaxed fibres partially cover each other. Even high waves of contraction exhibit, in comparison with the relaxed portions of the fibre, little or no alteration qua increase or decrease of colour, in the ascending or descending stages. This leads us to infer that in contracted muscle-fibres the increase of colour which should go along with n A the thickening of the fibre is compensated, Dr- over-compensated, by a diminution of the double refraction coincident with the con- traction. The method of polarised light enables us further to form a conclusion with regard to another important point in the behaviour of striated muscle-fibres during contraction. If the height of the metabolous and arimetabolous segments is compared in an appropriate pre- paration (Fig. 32) with crossed prisms, during the transition from the relaxed to the contracted portions of the fibre, it may be seen that with increasing contraction the height of the iso- tropous (arimetabolous) segments diminishes more than that of the anisotropous (metabol- ous), so that the volume of the latter increases at the expense of the former, the total volume of the section in question, like that of the entire fibre, remaining constant. Engelmann has established these facts in appropriate objects by micrometric measurements. In order to explain the effect he assumes that fluid passes from the isotropous to the anisotropous substance in contraction ; the anisotropous substance swells, the isotropous shrinks. This water-exchange between the metabolous and arimetabolous segments must natur- ally be imagined as be
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