. A healthy body. A textbook on anatomy, physiology, hygiene, alcohol, and narcotics. For use in intermediate grades in public and private schools . Fig. 14. The muscles of thearm, ending in the white ten-dons at the wrist. classes, Two Kinds of Muscle. Themuscles are divided into twothe voluntary, and the involuntary. THE MUSCLES. 49 We can move some muscles whenever we wish, asthose of tlie face and the arm. Because we are thusable to control their move-ments, they are called vol-untary. But some musclescannot be controlled in thisway. They do their workwhether we wish it or cannot co
. A healthy body. A textbook on anatomy, physiology, hygiene, alcohol, and narcotics. For use in intermediate grades in public and private schools . Fig. 14. The muscles of thearm, ending in the white ten-dons at the wrist. classes, Two Kinds of Muscle. Themuscles are divided into twothe voluntary, and the involuntary. THE MUSCLES. 49 We can move some muscles whenever we wish, asthose of tlie face and the arm. Because we are thusable to control their move-ments, they are called vol-untary. But some musclescannot be controlled in thisway. They do their workwhether we wish it or cannot control their move-ments by the will, so theyare called involuntary. Themuscles of the stomach andthe heart are of this heart beats and the stom-ach contracts, and we have nopower to stop The Uses of Muscle. Nearlyall the voluntary muscles areattached to bone at each end;it is because they contract andmove the bones that we are able to run and jump and perform all the movementsof which the body is capable. Fig. 15. Yohmtary muscle,with its blood-vessels. (1) themuscle fibres ; (2) the blood-ves-sels, magnified. The Structure of Muscle. If a piece of boiled, leanmeat, which is voluntary muscle, be examined, it willbe noticed that it readily falls apart into little threadsof tissue ; and with needles these little threads maybe easily divided into still smaller threads. If one 4 50 A HEALTHY BODY. of these small threads be placed under the microscope it will be found to consist of many small fibres. (Fig. 15.) Therefore we say that voluntary muscle is made up of many small fibres, all bound together. Our illustration shows four of these fibres, and also the blood-vessels that belong to them. Involuntary muscle is composed of very small cells which are placed close togethe
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