MOTION AND LOCOMOTION. 153 



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 vio- 

 lently 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 crouch- 

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

 the Body balanced on the toes. The centre 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 inclined in that direction; and in jumping ver- 

 tically 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 gener- 

 ally, so that they shall be supplied with proper materials for 

 growth and repair, and have their wastes rapidly and effi- 

 ciently removed. In other words, good food and pure air are 

 necessary for a vigorous muscular system, a fact which train- 

 ers recognize in insisting upon a strict dietary, and in super- 

 vising 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, 

 exercise is the necessary condition of their best development. 

 A muscle which is permanently unused degenerates and is 

 absorbed, little finally being left but the connective tissue of 

 the organ and a few muscle fibres filled with oil-drops. This 

 is well seen in cases of paralysis dependent on injury to the 



