In the very tiny infant then of a few weeks old, nothing stops the foot from making the most acute angle with the leg except contact. The child a year or so old has lost some of this freedom, and begins to be adapted for the upright position; later on will begin to “feel its feet,” as the nurses say, and soon to rear itself upon its hind-limbs. The infant’s foot is plantigrade, and gradually during growth becomes adapted for the erect posture, and loses freedom of movement as it gains in strength.
FOOT OF AN INFANT NEARLY A YEAR OLD.
On pressure with the finger the angle of the foot with the leg is less acute and more adapted for the erect posture.
In the adult, in order to measure the angle required, it is necessary to get the long axis of the leg and the long axis of the foot, and then take the angle both when the foot is pressed upon and also when no pressure is permitted. To obtain this angle shadows may be tried; photographs are good, from which diagrams may be made with tracing paper and pencil; also mechanical plans, such as placing the back of the leg on a plane surface (as a table) allowing for the calf by a block behind the ankle, and then pressing a thin board against the sole of the foot, measuring with a suitable instrument the angle the board makes with the table at moments of extreme position, both with pressure and without. With the sole of the foot on the floor, and the heel well down when the leg is carried forward to the extreme position, the angle that the leg makes with the floor will indicate sufficiently, much as is shown in the picture of sitting down using only one limb. Whatever method is used the result is only approximate, but they will all agree, and are sufficient for our purpose. The measurements made when the feet are pressed gives alike in the Swiss guides and in the adult amateur an angle of about 60 degrees; without pressure the angle is nearer 70 degrees, and I measured two rowing men who could get no more acute angle than 70 degrees under any conditions. Always remembering that there is a fairly considerable “personal equation,” we may conclude that if there be any difference between guides and amateurs it will not be enough at any rate to explain more than a trifling part of the superiority of the guides in walking up a slope. The height of the boot heel may be taken to be the same in all mountain boots, but the guides tend to wear heels rather high.
FOOT OF AN INFANT NEARLY A YEAR OLD.