MUSCLES AND PHENOMENA OF CONTRACTION. 141 



the hand where the weight rests to be fourteen inches, and 

 the distance of the point where the biceps muscle is attached 

 to the radius, to be three inches from the elbow. With 

 what power would the biceps muscle have to contract to 

 raise fifty pounds in the hands? In this case the power-arm 

 is three inches and the weight-arm fourteen inches. By 

 the terms of the equation 3 x = 14 X 50 and x = 233 l7 3 

 pounds. In this case much power is lost, for to lift but 

 the rather small weight of fifty pounds requires a pull of 

 233Va pounds of the biceps, and this on the supposition 

 that the biceps is pulling in the most advantageous direc- 

 tion, while as a matter of fact pulling at an angle adds a 

 further disadvantage. But while much power is lost in this 

 way, but a slight contraction of the biceps moves the hand 

 through a much greater distance. By means of these var- 

 ious levers all through the body we are enabled to accom- 

 plish the familiar movements of walking, running, jumping, 

 swimming, and so on. The exact manner in which these 

 various movements are brought about may be so easily de- 

 termined by direct observation that a full discussion of them 

 is here omitted. 



The Hygiene of Muscles. 



There are but two things in the body which are under 

 our immediate control. One of these is the system of vol- 

 untary muscles, and the second is the central nervous sys- 

 tem. These two systems are placed in our own hands, and 

 for the growth and development of them, we ourselves are 

 directly responsible, and as on the development of these 

 two systems nearly all the other systems depend, we are 

 enabled in an indirect way to be masters of our whole 

 frame. There are, therefore, but two kinds of exercise 

 under our immediate control muscular exercise and nerv- 

 ous exercise. Two kinds of education or, rather, two 

 phases of the same education are, therefore, possible, a 

 physical education and the education of the mind. No one 

 questions for a moment that the mind, if left to itself to 



