It will be found true, we believe, that in persons of muscular temperament—the temperament that gives tall, spare, and angular forms—the curvature of the arch is greater than in those whose natural disposition of body is toward fleshiness. In the latter case, the muscles of the whole system being weaker, they allow the bones of the foot to separate more easily, and this, consequently, allows the flattening. In other words, we strongly suspect that in this temperament of the body the ligaments are not so dense, firm, and strong as they are in persons whose physical structure is more predominantly muscular. The ligaments which hold the bones together at the joints are not designed to stretch, under ordinary circumstances, but they do yield when sufficient force is exerted upon them, as in the case of sprains and dislocations, and it is reasonable to infer that they adapt themselves to the demand made upon them. The muscles grow longer and larger, as do also the bones, under circumstances that call for such growth or adaptations to conditions. So do _all_ the organs and tissues of the body, in greater or less degree; and if the ligaments do not, they are a plain exception, which is not probable. This being so, a constant strain upon the ligaments of the foot’s arch, as in standing for several hours without rest, must cause them to stretch somewhat, allowing the bones to loosen and sink down, while the same severe strain, if continued for a yet longer period, would force them to grow into this lengthened condition, to meet the demand upon them, thus rendering the fault permanent. In persons of fleshy tendency, the natural softness and weakness of the muscles and ligaments allow them the more easily to give way to the pressure upon the arch. It is believed to be the fact that the deformity is more common among people of this type, and it will be well for those so constituted to guard against anything that tends to its development. It is in persons of the opposite type—those who have firm, close, hard, and strong muscles, and no extra flesh—that the arch is found in its greatest perfection. There the strong muscles and ligaments bind the bones together with such firmness that the arch is enabled longer to resist the influences which tend to break it down. Yet the flat foot is very common, in spite of all nature’s efforts for prevention. The deformity, in greater or less degree, may be said to exist as the rule among adult persons, while the natural arch is the exception. Among some classes of people, flat-foot is almost wholly prevalent. Hard toil and degrading conditions not only debase the person morally and intellectually, but they affect the gait and carriage, and their influence may be seen to reach down to the very bottom of the foot.