42 MATERIALS FOR A MEMOIR OX 



in the hoofed. In backward movements tlie opposite obtains, for 

 in these positions the fore limbs can be carried back to a variable 

 distance. In the deer and its congeners, owing to the great 

 obliquity of the humerus, the fore foot can be brought to a point 

 near the centre of the body, and the limb be vertical. (See p. 92.) 

 In the horse the fore limb in backward strain is very oblique, 

 and the foot, while well placed under the trunk, cannot reach the 

 centre. In the baboon the fore foot cannot pass beyond a verti- 

 cal line which intersects the trunk a little back of the shoulder- 

 joint. The backward movement of the hind limb is nearly the 

 same in all animals. The leg is always carried in a direct path, 

 the limit of the movement being determined solely by the length 

 of the limb. In a word, the forward movement is the less con- 

 strained in the fore limb, while the backward movement is the least 

 constrained in the hind limb. The most variable movements are 

 the backward for the fore liml) and the forward for the hind limb. 



The "stroke," or period of impact against the ground, can be 

 divided into three stages, — first, that of forward movement, when 

 the foot rests against the ground, chiefly on the outer border (see 

 p. 50) ; second, the vertical position, when the weight is borne upon 

 the foot as a whole, or when the marginal toes are shorter than the 

 third and fourth upon the central portion ; and, third, the back- 

 ward movement, or backward strain, when the foot rests chiefly 

 upon the inner margin. I am informed by Dr. M. H. Cryer that 

 skaters invariably bring the skate "on" the ice by the outer edge 

 of the runner, and take it " otf " by the inner edge. Practically 

 the same motion is seen in swimming for both hands and feet. 



The fore leg may be said to be thrust forward as the hand is 

 thrust when used for grasping. The ground may be said to be 

 seized by the foot and the body pulled up to the point of pur- 

 chase. (See p. 52.) The hind leg (usually of the opposite side) 

 pushes the hind part of the body forward at the same moment. 

 As the fore foot passes its vertical it also would tend to push the 

 body, and in this way assist the hind leg. 



In clawed animals the seizing power is carried to a high state, 

 and in hoofed animals it remains at a low one. In all domesti- 

 cated animals the pushing power of the hind foot is unimpaired. 

 (See p. 92.) It is most modified in forms adapted for tree life, 

 as the ape and the sloth. 



