Although the heels follow one another in a line the toes diverge a little from the line, because the foot slants, as I have just said, somewhat _out_wards when it is placed upon the ground. It results from this position of the foot that the weight of the body descends upon it with a slight obliquity, _in_wards as well as forwards; and that is precisely the direction in which the foot is best prepared to receive weight. For, when the foot rests upon the ground in this position all the ligaments on the inner side (and they are very strong) as well as those beneath, are on the stretch; and the joints, with the exception of the ankle-joint, are as it were locked, so as to afford a secure, steady basis of support to the leg. When the weight of the body descends upon the foot in the direction mentioned a sprain rarely occurs. It is when the weight falls in the opposite direction, that is, more or less obliquely _out_wards, and throws the ankle out, that a sprain easily happens. Thus a slight inequality of the ground, or any other cause that tilts up the inner edge of the foot, is likely to lead to a sprain, especially when we are going down hill or down steps. Here let me remark that a SPRAIN is the result of a stretching of some ligament, or other part, caused by an undue force being brought to bear upon it. The ligaments are very strong, and under ordinary circumstances are not very sensitive; and they are capable of offering great resistance to force applied in the direction in which they are calculated to meet it. But, if the force be applied in a direction in which they are not calculated to meet it, they are easily injured, and they become, then, very painful. The same is, also, likely to occur if the force be severe or sudden. The muscles are a very great assistance to the ligaments, forasmuch as, by placing and retaining the joints in proper positions, they regulate the direction in which forces are brought to bear upon the ligaments. Moreover, by steadying or bracing the joints, they check or break the force and prevent its being suddenly imposed upon the ligaments. And the muscles, by virtue of their contractile property, have the capability of becoming tight in any position of the joint, which is an immense advantage; whereas a ligament having no contractility and, usually, no elasticity, is tight only in one position. The office of a ligament is to limit the movement of a joint in a particular direction; and, till the joint has assumed a certain position--till it is bent or straightened to a certain angle--the ligament does not come into play. During the bending or straightening of a limb the muscles regulate the movement, and bring it to a stop or check it before it has gone to its full extent; and, thus, the ligament is relieved from that sudden imposition of force which would result if it were required to check the movement of a joint in its full swing.