LOCOMOTOK MECHANISMS. 831 



foot has reached the ground, there being an interval during which neither 

 foot is on the ground, the person is said to be running, not walking. 



In jumping, this propulsion of the body takes place on both feet at the 

 same time ; in hopping, it is effected on one foot only. 



774. The locomotion of four-footed animals is necessarily more com- 

 plicated than that of man. The simple walk, such as that of the horse, is 

 executed in four times, with a diagonal succession ; thus, right fore-leg, left 

 hind-leg, left fore-leg, right hind-leg. In the amble, such as that of the 

 camel, the two feet of the same side are put down at one and the same time, 

 this movement being followed by a similar movement of the other two legs ; 

 it corresponds, therefore, very closely to human walking. In the trot, which 

 corresponds to human running, the two diagonally opposite feet are brought 

 to the ground at the same time, and the body is propelled forward on them. 

 Concerning this, however, as well as concerning the still more complicated 

 gallop and canter, observers are not agreed, and much discussion has arisen. 



The other problems connected with the action of the various skeletal 

 muscles of the body are too special to be considered here. 



