DISTURBANCES IN POSTEMBRYONIC DEVELOPMENT OF THE FOOT Pathology of the Commencement of develop ment of the foot from the embryonic mass in the first few weeks of em bryonic life is soon followed by the formation of the lower leg and finally of the thigh. On the fifteenth day conditions are further advanced and after a month all bones present a fibrous structure, but separation into single parts is still lacking. This division and the formation of cartilage in the different parts of the skeleton occur during the first few months, and such torsions take place as the attached fin must of necessity per form in order to occupy later the position of a human leg and foot. The rotation is limited as a rule to the hip and femur. However, both tibia and fibula present a mild degree of crossing and the foot assumes all entirely supinated attitude. The soles of the feet face each other, most children being horn in that condition. All motions originate [coin this attitude, club-foot in extreme form, but the foot always returns to the position from which it started. This attitude is habitual in SO per cent. of infants; in the remaining 20 per cent. the attitude of the foot varies by indifferent degrees even to the anomalies which we term con genital flat-foot and talipes caleaneus The foot of the newborn is very delicately formed awl its different joints are very flexible. Most conspicuous is the finger-like flexibility of the toes (ability to abduct the big toe). When a foot is surrounded by a great quantity of fatty tissue it appears to be flat, a condition which has given rise to the contention that all the newborn had flat feet. I have proved by means of frozen sections of specimens that the osseous structures of the normal arch of the foot are alike in the newborn and 41 adults. Apparently flatness is produced wholly by the surrounding fatty tissue. If the child becomes thinner (atrophy) the arch of the foot presents itself immediately after the disappearance of the fat (impression of the sole).
Conditions remain stationary during the period of infancy. Later on, with increasing corpulence the foot apparently again becomes more flat.
A child starts some kind of locomotion (luring the seventh and eighth months. It should normally be the kind of motion which in the history of mankind preceded the erect posture and gait.
Creeping. — Healthy children, when left • to themselves, generally adopt this kind of locomotion. It should be encouraged by all means, because it meets the natural requirements and trains the bones, muscles, and joints to bear weight later on. Suppression of this period of creep ing must be considered a severe educational mistake.
Where children are taught to stand on their feet too early the untrained muscles, bones, and ligaments yield to the overweight and deformities of the foot are produced, the marked degrees of which we term fiat-foot.
The weight forces the astragalus forward and downward upon the oblique articulating surface of the os calcis, at the same time calling forth an outward rotation of the astragalus. This intended torsion is communicated to the other bones of the foot, resulting in a turning of the foot outward. The inner border of the astragaloid trochlea endures more weight, the os caleis is turned outward, and we are face to face with a condition which we term pronated foot or Hat-foot (see section on Flat-foot).
Even in a normal foot the period when a child begins to walk is a critical one. The arch of the foot is distinctly lowered during the first half of the second year. The head of the astragalus and the scaphoid bone force the fatty tissue downward (physiological prominence). With the beginning of the third year the foot becomes strong enough to elimi nate the lowering of the arch. Because the period of the first corpulence passes at this time, the foot begins to appear more hollow and the impres sions of the sole resemble more and more those of adults.