An elementary physiology and hygiene for use in upper grammar grades . direction. We can lift the arm above the head, to thefront, to the side, turn it around, and bend it backwardas far as the hinge joint at the elbow will allow. Thetwo bones which form the shoulder joint are the shoulder blade, or scapula,and the upper arm bone,or humerus. The shapesof these bones may be seenfrom Figure 53. As is evident from theillustration, the shoulderblade has a somewhatrounded hollow. The up-per end of the arm boneis rounded like a balland fits into this socket orhollow. Since the end ofthe arm bone is
An elementary physiology and hygiene for use in upper grammar grades . direction. We can lift the arm above the head, to thefront, to the side, turn it around, and bend it backwardas far as the hinge joint at the elbow will allow. Thetwo bones which form the shoulder joint are the shoulder blade, or scapula,and the upper arm bone,or humerus. The shapesof these bones may be seenfrom Figure 53. As is evident from theillustration, the shoulderblade has a somewhatrounded hollow. The up-per end of the arm boneis rounded like a balland fits into this socket orhollow. Since the end ofthe arm bone is a ball, and the socket in the shoulderblade is a hollow cavity, the arm can be moved in alldirections. It is this shape of the bones that gives usour great freedom in lifting the arms. The ends of thebones are not only rounded, but they are made particu-larly smooth by being covered with cartilage, and theyare also moistened with liquid like that in the hingejoint. The bones are bound together at the shoulder by justsuch strong bands as we saw at the knee. There is,. Fig. 53. — The Bones of theShoulder Joint.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectphysiology, bookyear1
