. A healthy body. A textbook on anatomy, physiology, hygiene, alcohol, and narcotics. For use in intermediate grades in public and private schools . s the front of theknee-joint. There are a number of small bones in the foot, ar-ranged, as in the case of the wrist and the hand, so asto render a variety of movements possible. The Arch of the Foot. The bones of the foot are soput together that they form an arch, so that only thefront and the back of it touch the floor. This archis useful in protecting the body from too severe a shockwhen one is running or jumping ; for when the weightof the body
. A healthy body. A textbook on anatomy, physiology, hygiene, alcohol, and narcotics. For use in intermediate grades in public and private schools . s the front of theknee-joint. There are a number of small bones in the foot, ar-ranged, as in the case of the wrist and the hand, so asto render a variety of movements possible. The Arch of the Foot. The bones of the foot are soput together that they form an arch, so that only thefront and the back of it touch the floor. This archis useful in protecting the body from too severe a shockwhen one is running or jumping ; for when the weightof the body is thrown upon the arch, its centre is presseddownward, and thus it acts like a spring. 38 A HEALTHY BODY. The Joints. There may be only two, or there may bemany bones forming a joint. The Joints are oiled. On the endsof the bones which come to-gether to make a joint there is akind of gristle, called cartilage/ This iscovered with a verythin membrane,which is constantlysecreting, or pouringout, a watery sub-stance. This sub-stance, called thejoint-water, servesthe same purpose thatoil does when it is putupon the joints orwheels of Fig. 12. A sectionthrough the inside of the endof the femur is seen toconsist of loose, spongy-bone. The solid out-side is becoming thickerat the lower part. If the membrane covering thecartilage should become inflamed or injured in anyway, it might fail to furnish enough of this fluid;then the movements of the joint would be painful,and the joints themselves would become stiff and mis-shapen. The Ligaments. The bones are held in place at thejoint by means of white, shining bands of tissue called^ ligaments. A sprain is an injury to the liga-ments. THE SKELETON AND THE JOINTS. 39 Tight and Loose Joints. The ligaments of some personsare very firm, and the joints are not easily moved. Inothers the ligaments are not so firm, and the joints aremore easily moved. We say of these latter that theyare - loose-jointed. When a bone ge
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