The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . ere are two kinds of muscles in the body,called voluntary and involinitary, which differ verymuch in their structure and functions. The volun-tary muscles, as the name implies, are under the con-trol of the will; while the involuntary muscles arenot only beyond our control, but act as a rule with-out our knowledge or consciousness. 3
The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . ere are two kinds of muscles in the body,called voluntary and involinitary, which differ verymuch in their structure and functions. The volun-tary muscles, as the name implies, are under the con-trol of the will; while the involuntary muscles arenot only beyond our control, but act as a rule with-out our knowledge or consciousness. 37. The Voluntary Muscles.—A vohtntary muscleis a mass of reddish fibers, somewhat loosely joinedtogether by connective tissue, and easily separatedlengthwise.* The fiesh of animals is composed ofmuscular tissue. Every voluntary muscle is united * If the fibers of a piece of lean meat are carefully separated andclosely scrutinized, it will be seen that they are connected with eachother by a delicate tissue of fine white threads, interwoven like thefibers of a cobweb or of the most delicate lace-work. This is calledconnective tissue, and is found in almost all parts of the body, unitingthe different elements that make up the various organs. THE MUSCLES. 33. Fig. a.—The muscular system. 34 ORGANS OF MOTION. Sit each end to some fixed point in the body, andthere is always a joint or point of flexure betweenits points of attachment. When the muscle con-tracts, therefore, the two ends are brought nearertogether, and motion is produced in the organ orlimb to which it is attached. Every voluntary muscle can be divided intosmall fibers, lying side by side, and these again intofibrils still more minute. Each fibril under themicroscope presents an appearance of delicate linesrunning at right angles to its length (Fig. i6).
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