. The crayfish : an introduction to the study of zoology . Crayfish. 102 THE PHYSIOLOGY OF THE COMMON CRAYFISH. (fig. 23). The nerve bundle which passes to a muscle breaks up into smaller bundles and, finally, into separate fibres, each of which ultimately terminates by becoming continuous with the substance of a muscular fibre fig. 19, F.) Now the peculiarity of a muscle nerve, or motor nerve, as it is called, is that irritation of the nerve fibre at any part of its length, however distant from the muscle,. Fig. 23.— Astacus flwviatilis.—Three nerve fibres, with the connective tissue in which
. The crayfish : an introduction to the study of zoology . Crayfish. 102 THE PHYSIOLOGY OF THE COMMON CRAYFISH. (fig. 23). The nerve bundle which passes to a muscle breaks up into smaller bundles and, finally, into separate fibres, each of which ultimately terminates by becoming continuous with the substance of a muscular fibre fig. 19, F.) Now the peculiarity of a muscle nerve, or motor nerve, as it is called, is that irritation of the nerve fibre at any part of its length, however distant from the muscle,. Fig. 23.— Astacus flwviatilis.—Three nerve fibres, with the connective tissue in which they are imbedded. (Magnified about 250 dia- meters.) 7t, nuclei. brings about muscular contraction, just as if itself were irritated. A change is produced in the mole- cular condition of the nerve at the point of irritation; and this change is propagated along the nerve, until it reaches the muscle, in which it gives rise to that change in the arrangement of its molecules, the most obvious eifect of which is the sudden alteration of form which we call muscular contraction. If we follow the course of the motor nerves in a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Huxley, Thomas Henry, 1825-1895. London : Kegan Paul, Trench, Tru?bner & Co.
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