MAN MADE TO STAND ERECT. 



body would take the position of that of a quadruped, in which the 

 spinal column would be horizontal, the upper part of the trunk 

 being supported by the arms, the hands performing the duties of fore- 

 feet. But this is prevented by the establishment along the whole- 

 extent of the back of several layers of powerful muscles, which tie 

 the vertebrse together, two and two, three and three, four and 

 four, and so on. The tone of these muscles is such, that their 

 normal tension produces a force which equilibrates with the 

 weight of the trunk acting at its centre of gravity in front of the 

 spine. These muscles have a power of contraction and relaxation 

 within certain limits, by which the body can be inclined back- 

 wards or forwards, more or less. The head is mounted upon the 

 summit of the vertebral column, forming as it were its capital, in 

 a manner obviously adapted for the vertical position. Like the 

 trunk, its centre of gravity is a little in front of the summit to 

 the spinal column, and therefore it would have a tendency to 

 incline forwards, but this as before is resisted by muscles of 

 adequate power placed on the back of the neck. 



Nothing more manifestly indicates the intention of nature 

 that man should stand erect, than the position of his face 

 and the direction of his optic axes. In the erect position his 

 face looks forwards, and the optic axes are horizontal. But 

 if he were to assume the prone position, supported by his four 

 members like a quadruped, the optic axes would be directed 

 downwards, and, except by a strained effort of the neck, he 

 could not see before him. To this it may be added, that 

 the knee joint being so constructed that the leg can only be 

 deflected backwards on the thigh, would render the legs utterly 

 unfitted to be members of support and locomotion in the prone 

 position, since in that case the point of support would be, not the 

 feet, but the knees. Now, independently of the consideration that 

 in this case the legs and feet would not only become useless, but 

 would be an impediment to every act of locomotion, the shortness of 

 the thigh would inconveniently limit the power of progression, the 

 thin integuments covering the knee-pan would soon be destroyed 

 by the pressure upon it, and the knee-pan itself, a loose and de- 

 tached bone, would be displaced, and the members totally disabled. 



It would not be worth while to insist upon these particulars, 

 were it not that some authors, impelled doubtless by the love of 

 paradox, have maintained that the prone position is natural to 

 man, and the erect position the result of education. 



16. Man, then, alone presents the characters of a bimanous and 

 bipedous animal. The various species of apes, who approach so 

 close to him in some respects, differ from him essentially in their 

 members, their inferior or posterior members having as much the 



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