MOTION AND LOCOMOTION 111 



foot reaches the ground. When the rear foot is to leave the sup- 

 port, the knee is suddenly straightened, and at the same time the 

 ankle-joint is extended so as to push the toes forcibly on the 

 ground and give the whole Body a powerful push forwards and 

 upwards. Immediately after this the knee is greatly flexed and 

 the foot raised from the ground, and this occurs before the toes of 

 the forward foot reach the latter. The swinging leg in each step 

 is violently pulled forwards and not suffered to swing naturally, 

 as in walking. By this the rapidity of the succession of steps is 

 increased, and at the same time the stride is made greater by 

 the sort of one-legged leap that occurs through the jerk given by 

 the straightening of the knee of the rear leg just before it leaves 

 the ground. 



Leaping. In this mode of progression the Body is raised 

 completely from the ground for a considerable period. In a 

 powerful leap the ankles, knees, and hip-joints are all flexed as a 

 preparatory measure, so that the Body assumes a crouching 

 attitude. The heels, next, are raised from the ground and the 

 Body balanced on the toes. The center of gravity of the Body 

 is then thrown forwards, and simultaneously the flexed joints 

 are straightened, and by the resistance of the ground, the Body 

 receives a propulsion forwards; much in the same way as a ball 

 rebounds from a wall. The arms are at the same time thrown 

 forwards. In leaping backwards, the Body and arms are in- 

 clined in that direction; and in jumping vertically there is no 

 leaning either way and the arms are kept by the sides. 



Hygiene of the Muscles. The healthy working of the muscles 

 needs of course a healthy state of the Body generally, so that 

 they shall be supplied with proper materials for growth and re- 

 pair, and have their wastes rapidly and efficiently removed. In 

 other words, good food and pure air are necessary for a vigorous 

 muscular system, a fact which trainers recognize in insisting upon 

 a strict dietary, and in supervising generally the mode of life of 

 those who are to engage in athletic contests. The muscles should 

 also not be exposed to any considerable continued pressure, since 

 this interferes with the flow of blood and lymph through them. 



As far as the muscles themselves are directly concerned, exer- 

 cise is the necessary condition of their best development. A 

 muscle which is permanently unused degenerates and is absorbed, 



