So leaving out of the question all lateral movements at the ankle-joint as difficult and complicated to estimate, we will briefly consider the question of the ordinary angle that the foot makes with the leg so far as it is less than a right angle, and whether the trained guide has any advantage over the amateur in this respect.
FOOT OF AN INFANT FIVE WEEKS OLD, SHOWING THE INSTEP TOUCHING THE SHIN ON SLIGHT PRESSURE OF THE FINGER.
The adaptation of the foot for progression on all fours. The baby is wrapped in a napkin and black velvet, and held by a nurse.
To begin with the foot of an infant, we notice that the foot, like the hand, is all adapted for climbing. Dr. Louis Robinson has shown that the infant’s hand-grip is so strong, that the whole weight of its body can be borne by the prehensile power of the hand. The miner in Bret Harte’s The Luck of Roaring Camp realized this strength of grip when he said after an experience with a cradled infant, “He wrastled with my finger, the d——d little cuss!”
The following photographs show how the child’s foot can be made by a touch of the forefinger to approximate the instep to the leg until there is actual contact. The toes curl round to take a great grip of the object pressing against the sole, and generally speaking there is the most wonderful adaptation both for climbing and for progression on all fours.
The infant chosen for the first photograph was rather an unusually thin baby, but it had a fair amount of vitality, and illustrates better than a chubby child the points which it is necessary to bring out. If, with tracing paper placed over the picture, a pencil line be drawn along the bearing surface of the sole of the foot, and another along the leg to meet the former line below the heel, the angle made by these two lines will measure about twenty degrees.