349 



(CLXXXI.) nor can we admit that man might walk on all fours all his 

 lite, if he were not broken of the bad habit which he learns in infancy. 



CLXXXII1. Very little has been added to what Galen has said in his 

 admirable work of the structure of parts, relative to the respective ad- 

 vantages attending the peculiar conformation and structure of the upper 

 and lower limbs. It is easy to see, that in combining, as much as pos- 

 sible, strength and facility of motion, Nature has made the former pre- 

 dominate in the structure of the inferior extremities, while she has sacri- 

 ficed strength to facility, to precision, to extent, and rapidity of motion, 

 in the upper extremities. 



To convince one's self of the truth of what has been stated, it is suffi- 

 cient to compare, under the two relations* of the resistance of which 

 they are capable, and of the motions which they allow, the pelvis to the 

 shoulder, the thigh to the humerus, the leg to the fore arm, and the foot 

 to the hand. 



The inferior extremities, if examined when the bones are covered with 

 the soft parts, will present the appearance of an inverted cone or pyramid, 

 which, at first sight, appears contrary to the object which Nature had in 

 view; but if the bones be stripped of their fleshy coverings, these solid 

 supports will be seen to represent a pyramid, whose base is at the lowest 

 part, and formed by the foot, and which decreases in breadth upward 

 from the leg, formed by the union of two bones, towards the thigh, con- 

 sisting of only one bone. 



If it be asked why the inferior extremities are formed of several pieces, 

 detached and placed one above the other, it will be found that they are 

 thereby much more solid, than if formed of one bone, since, according to 

 a theorem, demonstrated by Eulerf two columns containing the same 

 quantity of matter, and of equal diameter, have each a solidity in inverse 

 ratio of the squares of their height; in other words, of two columns, con- 

 taining the same materials, of equal diameter, and of unequal height, the 

 smaller is the stronger. 



The long bones, which by their union form the inferior extremity, con- 

 lain a cavity which adds to their strength, for, according to another theo- 

 rem, explained by Galileo, two hollow columns of the same quantity of 

 matter, of the same weight and length, bear to each other a proportion of 

 strength measured by the diameter of their internal excavations. 



The breadth of surface of the articulations of the inferior extremities, 

 assists, materially, in giving them additional strength, when in standing^ 

 these bones are in a vertical direction. No articulation has a broader 



* See the anatomical observations on the neck of the thigh bone, which I have pre- 

 fixed to a memoir which bears the title of Dissertation anatorrdco-chimrgicale sur Ics frac- 

 tures du col de femur. Paris an VII. 



} J\lelhodiis inrt-.nientli Eneas citrvas. 



Nature has, therefore, increased the number of these columns in the extremities of 

 quadrupeds, by raising their heel and the different parts of the foot, whose bones she 

 has lengthened, to make of them so many secondary legs. These numerous columns 

 placed above one another, are alternately 'inclined, and in a state of habitual flexion, in 

 the quadrupeds remarkable for swiftness in running, or for their power in leaping, as in 

 the hare and squirrel, while in the ox, and especially in the elephant, they are ,all placed 

 vertically, so that the enormous mass of the latter rests on four pillars, the different 

 pieces of which are short, and so slightly moveable on one another, that, as Barthex. 

 observes, Saint Basil has adopted the error of Pliny, JElian, and several other wri- 

 ters of antiquity, that there are no articulations in the legs of that monstrous animal- 

 Author's Note. 



