IN THE HUMAN FRAME. 
69 
The joint at the shoulder compared with the joint at the 
hip , though both ball and socket joints, discovers a differ¬ 
ence in their form and proportions, well suited, to the dif¬ 
ferent offices which the limbs have to execute. The cup 
or socket at the shoulder is much shallower and flatter 
than it is at the hip, and is also in part formed of cartilage 
set round the rim of the cup. The socket, into which the 
head of the thigh-bone is inserted, is deeper, and made 
of more solid materials.* This agrees with the duties as- 
advantages of the structure of the foot, since we stand upon an elastic 
arch, the hinder extremity of which is the heel, and the anterior the balls 
of the toes. A finely formed foot should be high in the instep. The 
walk of opera dancers is neither natural nor beautiful; but the surprising 
exercises which they perform give to the joints of the foot a freedom of 
motion almost like that of the hand. We have seen the dancers, in their 
morning exercises, stand for twenty minutes on the extremities of their 
toes, after which the effort is to bend the inner ankle down to the floor, 
in preparation for the Bolero step. By such unnatural postures and ex¬ 
ercises the foot is made unfit for walking, as may be observed in any of 
the retired dancers and old figurantes. By standing so much upon the 
toes, the human foot is converted to something more resembling that of a 
quadruped, where the heel never reaches the ground, and where the paw 
is nothing more than the phalanges of the toes. 
This arch of the foot, from the heel to the toe, has the astragalus, re¬ 
sembling the keystone of an arch; but, instead of being fixed, as in ma¬ 
sonry, it plays freely between two bones, and from these two bones, a 
strong elastic ligament is extended, on which the bone rests, sinking or 
rising as the weight of the body bears upon it, or is taken off, and this it 
is enabled to do by the action of the ligament which runs under it. 
This is the same elastic ligament which runs extensively along the back 
of the horse’s hind leg and foot, and gives the fine spring to it, but which 
is sometimes ruptured by the exertion of the animal in a leap, producing 
irrecoverable lameness. 
Having understood that the arch of the foot is perfect from the heel to 
the toe, we have next to observe, that there is an arch from side to side; 
for when a transverse section is made of the bones of the foot, the ex¬ 
posed surface presents a perfect arch of wedges, regularly formed like the 
stones of an arch in masonry. If we look down upon the bones of the 
foot, we shall see that they form a complete circle horizontally, leaving 
a space in their centre. These bones thus form three different arches— 
forward; across; and horizontally: they are wedged together, and bound 
by ligaments, and this is what we alluded to when we said that the foun¬ 
dations of the Eddystone were not laid on a better principle; but our ad¬ 
miration is more excited in observing, that the bones of the foot are not 
only wedged together, like the courses of stone for resistance, but that 
solidity is combined with elasticity and lightness. 
Notwithstanding the mobility of the foot in some positions, yet when 
the weight of the body bears directly over it, it becomes immovable, and 
the bones of the leg must be fractured before the foot yields. 
Bell's Treatise on Animal Mechanics . 
* The socket for the head of the thigh-bone is indeed deeper than that 
at the shoulder, but the “ materials ” which form the concavities are the 
