150 



HUMAN BIOLOGY 



accidents to the skeleton, medical assistance should be summoned 

 and the following directions carefully followed: (1) the sprained 

 member should be placed at once in cold water or in hot water 

 and held there for some time ; (2) arnica or witch hazel may be 

 appUed; (3) the sprain should then be boimd in a tight bandage 

 (these three applications tend to keep down the swelling) ; and 

 (4) (most important of all) the joint should have complete rest until 

 all swelling and soreness have disappeared. It is probable that more 

 permanent injuries result from careless treatment of sprains than 

 from aU other accidents to the skeleton. 



attachmenta of 

 tendons to 

 radius 



attachment of 

 tendons to 

 shoulder 



III. The Muscles 



220. Importance of muscle tissue. — Muscle tissue constitutes 

 41 per cent, or almost half, of the weight of the human body. In this 



kind of tissue is found one 

 fourth of aU the blood. But 

 the importance of muscle 

 tissue is appreciated, even 

 more fuUy, when we reaUze 

 that practically every kind 

 of movement in the body is 

 due to the action of the mus- 

 cles. Not only do they bring 

 about the more obvious mo- 

 tions of the arms (Fig. 47) , the 

 legs, the trunk, and the head, 

 but also the contractions of 

 the heart, of the stomach, and 

 of the other internal organs. Every change in the expression of the 

 face, and every variation in the tone of the voice, is likewise a result 

 of the action of this all-important tissue. Hence we are not sur- 

 prised that there are over five hundred separate muscles, which vary 

 in length from the fraction of an inch (within the ear cavity) to 

 over a foot and a half (down the front of the thigh). 



221. Kinds of muscle. — All of these muscles are in one way or 

 another under the control of the nervous system. Some of them are 



FlQ. 



elbow 

 47. — Action of biceps muscle. 



