114 



PHYSIOLOGY 



CHAP. 



standing, by throwing the weight of the body alternately on the 

 two feet. 



V. In locomotion there is a great and more or less rapid dis- 

 placement of the centre of gravity of the body and its base of 

 support. The movements performed by man in different forms 

 of locomotion are extremely complicated. But the principles of 

 mechanics by which we have explained the maintenance of 

 equilibration help to solve the fundamental problems of human 

 locomotion. 



The ordinary forms of locomotion are walking and running. 



In both the body is thrown 

 forward by the rhythmic and 

 alternate muscular contractions, 

 specially by the muscles of the 

 lower limbs. In walking the 

 body never leaves the ground, 

 but in running the whole body 

 is momentarily in the air. 



According to the description 

 of the Webers the lower limbs 

 are alternately active in walk- 

 ing ; while the one which is 

 applied to the ground sustains 

 the entire weight of the body 

 and throws the centre of gravity 

 forward, the other swings pass- 

 ively. 



Each step begins with plac- 

 ing the active limb with its sole 

 on the ground, the foot and 

 knee being somewhat flexed, 

 and the weight of the body 

 falls on the sole, while the 

 passive limb lies behind with 

 its great toe on the ground. At this stage the centres of the 

 femoral heads and the extremes of the two limbs form a rect- 

 angular triangle with the ground, two sides being formed by the 

 active limb and the ground, and the hypotenuse by the passive 

 limb (Fig. 73). 



In the next stage of the step, the knee of the active limb 

 is extended and the heel raised, throwing the centre of gravity 

 forward and slightly raising it, while at the same time the passive 

 leg is lifted from the ground and swung forwards till it once 

 more touches the ground and takes the weight of the body. 



According to the Webers each step in walking may be con- 

 sidered as a movement of falling forward, which is arrested by 

 advancing the passive limb and throwing the weight upon it. 



FIG. 73. Position of lower limbs at commence- 

 iment of the step. (Pick.) o, passive right 



leg which touches ground with big toe only ; 



db, left foot with whole sole resting on 

 i ground ; c, centre of rotation for hip-joint ; 



acd, rectangular triangle, in which the passive 

 !, limb forms the hypotenuse, the ground and 



active limb the catheter, according to the 



Webers' diagram. 



