LECTURE III. 145 



carpus in front, and which are usually called 

 the hocks. In those animals that leap to 

 great heights or distances, the os calcis pro- 

 jects, so as to form a most enormous lever, 

 and we judge of the animal's powers by 

 observing this projection. 



Such is the mechanism of our lower 

 limbs, nor need I endeavour to shew its 

 excellence, by the effects resulting from it. 

 Every one knows from what heights we can 

 leap, to what heights we can spring, and to 

 what distances we can bound, without in- 

 jury ; as well as how swiftly we can run, 

 how firmly we can stand, how nimbly we 

 can dance, and how perfectly we can ba- 

 lance ourselves upon the smallest surfaces 

 of support. Yet there are a few circum- 

 stances, which, I think, deserve consider- 

 ation. Gravitation seems to be the chief 

 cause which gives fixity of position to some 

 parts, and consequent freedom of motion 

 to others. When we stand upon one limb, 

 we balance our weight upon the head of the 

 thigh bone, and no effort is required to 

 maintain our position, but what is necessary 



L 



