■>ts 



372 THE MECHANICAL FtrNCTIONS. 



also for the lodgement of smaller muscles affixed to each in- 

 dividual joint, and for the protection of the various nerves 

 and blood vessels distributed to all these parts. The con- 

 cavity of the foot adapts it also to retain a firmer hold of the 

 inequalities of the ground on which we tread. The muscles 

 which raise the heel, and which compose the calf of the 

 leu, are of creat size and streno;th, and derive a considerable 

 increase of power from the projection of the bone of the 

 heel, into which their united tendons are inserted. In all 

 these respects the human structure possesses decided advan- 

 tages over that of the monkey, with reference to the specific 

 objects of its formation. 



It is impossible to doubt that nature intended man to as- 

 sume the erect attitude, when we advert to the mode in 

 which the head is placed on the spinal column. The enor- 

 mous development of the brain, and of the bones which in- 

 vest it, increases so considerably the weight of that part of 

 the head, which is situated behind its articulation with the 

 vertebrse of the neck, that the balance of the whole is much 

 more equal than it is in the monkey, where the weight of 

 the fore part very greatly preponderates. The muscles 

 which bend the head back upon the neck, and retain it in 

 its natural position, are therefore not required to be so pow- 

 erful as they must be in quadrupeds, especially in those 

 which graze, and in which the mouth and eyes must fre- 

 quently be directed downwards, for the purpose of procuring 

 food. In man this attitude would, if continued, be extreme- 

 ly fatiguing, from the weakness of those muscles, and the 

 absence of that strong ligament which sustains the w^elght 

 of the head in the ordinary horizontal attitude of quadru- 

 peds. 



"Pronaque cum spcclant anlmalia cxtera terram, 

 Os hominl sublime dedit, cxlumque tueri 

 Jusslt, et erectos ad sidera toilere vultus." — Otid. 



The space comprehended by the two feet is extremely 

 narrow, when compared with the extended base on which 

 the quadruped is supported. Hence, the stability of the body 



