490 EQUILIBRIUM OF ANIMALS : BASE OF SUPPORT. 



which its feet cover and inclose between them ; and the 

 wider this space, in proportion to the height of the centre of 

 gravity, the more stable will the equilibrium be, since the 

 body may be more displaced without being upset. Thus in 

 fig. 231 the table a must be upset ; because the line of direc- 

 tion e from the centre of gravity c falls outside the base of 

 support d ; whilst the table b, although equally inclined, will 

 not be upset but will return to its proper place, because the 

 line of direction e from its centre of gravity c falls within its 

 base d. Hence an animal which is supported upon four legs 

 will stand much more firmly than one which rests on two 

 only ; since its real base is the whole space included between 

 its four points of support. And again, an animal is more 

 firm when standing upon two legs, than when resting upon 

 one only. 



652. Moreover when an animal rests upon four legs, the 

 extent of its base is but little influenced by the size of the 



feet ; and thus to render them 

 broad would be to increase 

 their weight without adding 

 much to their use as supports. 

 This is easily understood by 

 comparing a quadruped to a 

 four-legged table ; if the legs 

 are sufficiently strong to support 

 the weight that rests upon 

 them, it matters little in regard 

 to the steadiness of the table, 

 whether they bear upon the 

 ground by mere points or by flat 

 surfaces j since it is the large sur- 

 face that would be enclosed by 

 lines joining them, which consti- 

 tutes the real base. Hence we 

 SE . find that, in most quadrupeds, 

 the limbs only touch the ground 

 by slightly-dilated extremities ; and the number of fingers is 

 reduced more and more, without diminishing their effect as 

 instruments of locomotion. Thus in Ruminant animals, as 

 the Deer, the number of toes is reduced to two in each foot, as 

 seen in fig. 232, where represents the tibia, ta the bones of 



Fig. 232. 

 FOOT OF DEEB 



233 



