198 



THE HUMAN SPECIES 



with a phase in which both feet are on the ground, the one leg 

 becoming perpendicular just as the other foot is about to leave 

 the ground. Moreover, when the left supporting leg is in the 

 act of thrusting forward the left side of the pelvis, the right arm 

 swings forward so as to re-adjust the centre of gravity. 



The trot in animals corresponds generally with running in 

 man, but there are certain contrasts due to differences in struc- 

 ture ; in trotting, the legs of quadrupeds swing in diagonal pairs, 

 while the other pair has not yet reached the ground. In man 

 there is a moment in the act of running when both feet are 

 simultaneously in the air, one foot having just left the ground 

 while the other has not reached it. 



The leap of quadrupeds, when the hind and fore- legs are 



FIGS. io6andiO7. How a man walks. (Munk-Schultz.) 



raised off the ground together, is only possible when the body 

 is upright. The leap in man may either be performed on the 

 same spot, or it may include a forward motion covering a con- 

 siderable distance : in the latter case the whole body- weight is 

 carried forwards, and the body is swung on a transverse axis. 



Swimming is effected in man by rapid kicking-out with the 

 feet backwards ; animals, however, paddle with all four legs at 

 once. 1 Most mammals can swim directly they find themselves 

 in the water : the mole, for instance, is an excellent swimmer. 

 Most apes, too, swim well, except a few of the baboons, and 

 among anthropoids the orang, gibbon and gorilla. These, if by 

 chance they fall into the water, sink and are drowned just like 

 the camel that makes no attempt to swim. 



1 Munk-Schultz, loc. cit., pp. 390-405. 



