It was this fault, possibly, which first suggested the practice of wearing heels, or, if it did not originate, at least continued it. _Heels partially restore that elevation and airiness of the foot which is given by a natural arch_, and which constitutes its grace and beauty. When rightly made, and worn as a choice of two evils, or as a partial remedy for an evil, they are not objectionable; but they can be only a partial corrective. They can never be substituted for a good arch; while, worn as they are and have been, _they really become one of the causes_ of the deformity which in turn calls for their use. Another cause is thus explained in Prof. Meyer’s book: “Flat-foot is occasioned by the loosening of the ligaments that knit the foot firmly together, and, by the consequent sinking of the arch, the inner aspect of the foot no longer presents the natural hollow in the sole. The causes of such loosening of the ligaments are numerous, but by far the most frequent, and one readily induced by the ordinary shoe, is weight improperly directed on the arch. If, for example, a shoe happens to be trodden on one side, and especially, as is most commonly the case, if it be so at the heel, then the heel has no support, except from the inner margin of the sole, which is thus worn away, and the heel-piece becomes oblique, or, in other words, lower at one side than the other. In walking and standing on such a heel-piece, the whole external margin of the foot is raised, and the inner, which naturally supports the arch, is so depressed as gradually to lose its convexity, and thus flat-foot is produced.” The nature of the cause here spoken of seems to be like that of a _sprain_, to a slight degree, and may be an influential one, but we doubt that it is the most common cause of that loosening of the ligaments which allows the foot to break down. The most common and efficient of all the causes of this difficulty, it appears to us, is the _short heel_ which has always been worn on boots and shoes, and is still, except where an innovation upon its shape has been made within a few years past. This, though not strictly a direct cause, like a strain from above, is the condition which most frequently admits and encourages the sinking of the arch. That _short heels_ most frequently admit of and encourage the sinking of the arch of the foot will be readily seen by an explanation. There are several bones which, together, form the forward part of the arch, while the back part consists of one larger bone, technically called the _calcaneum_, or _os calcis_, which makes up the principal part of the heel. Partly above this, and between it and the forward bones, is the one called the _astragalus_, which is the keystone, being located the highest of any, and the one upon which rest the bones of the leg; in size it is next to the _calcaneum_. An illustration will show the position. [Illustration: FIG. 27.