148 



ZOOLOGY. 



the pelvis, all that is required is to recline the body a little 

 to one side, so that the centre of gravity may fall on the sole 

 of the foot which receives the weight.* 



Most quadrupeds can neither 

 stand on one foot nor even on 

 the two hinder limbs; it is im- 

 possible for them to maintain, 

 excepting for a few seconds, 

 such a position; the base of 

 sustentation is too narrow; 

 their centre of gravity is to- 

 wards the chest, and the 

 muscles are not strong enough 

 to maintain the attitude. But 

 in man this position is easy, 

 natural, and belongs to him by 

 the character of his organiza- 

 tion. 



286. In the vertical posi- 

 tion it is chiefly the extensor 

 muscles which are called into 

 play; the limbs forming broken 

 levers become fixed ; the knee 



Fig. lOO.t 



Fig. 101. 



and ankle become immovable. 



287. Sitting is less fa- 

 tiguing than standing; but the horizontal position is that 

 alone which gives absolute rest to the body. 



288. Walking. When we walk, one of our feet is 

 carried forwards, whilst the other is extepded on the limb ; 

 and as this forcibly extended foot rests or presses against a 

 resisting soil, its elongation displaces the pelvis, and thus 



* Standing on one foot, using but little muscular effort, requires the 

 centre of gravity to be thrown forwards so as to fall towards the fore part of 

 the base of sustentation ; the knee tends then to bend backward, but is fixed 

 and rendered immovable by the- posterior ligament of Winslpw. Thus the 

 knee becomes fixed by a mechanical artifice requiring but little muscular 

 effort. But if we shift the centre of gravity so as to make it pass directly 

 through the joint, a strong muscular effort is required to fix the knee-joint ; 

 the extensor muscles are called into play in order to fix the patella, and the 

 position cannot in consequence be long maintained. E. K. 



t Fig. 100, hind foot of the horse. Fig. 101 , foot of the stag ; t, the tibia, 

 ta, first row of the bones of the tarsus ; ta, second row ; c, metatarsus or 

 cawowbone ; s, styloid bone formed by the skeleton of a rudimentary finger ; 

 there are two such ; p, proximal phalanx, called the great pastern ; pi, 

 middle phalanx (little pastern) ; pt, distal phalanx, or coffin-bone of veteri- 

 narians. 



