40 THYSIOLOGY OF MUSCLES AND NERVES. 



not always the same in the case of different muscles. On 

 comparing thick with thin muscles, it appears, in the first 

 place, that the extension in the case of thick muscles be- 

 comes less in proportion as the weight applied increases ; 

 and that the decrease in the height of elevation corre- 

 sponding to the increase in the weight applied proceeds 

 less rapidly ; so that much greater weights can be raised 

 by thick than by thin muscles. On the other hand, it 

 appears that in the case of muscles of equal thickness 

 the height of elevation is greater in proportion as 

 the muscle-fibres are longer. Under an equal weight 

 the height of elevation increases proportionately with 

 the length of the muscle-fibres. They decrease with 

 increased weight ; and they do this more rapidly in the 

 case of thin than of thick muscles. 



4. In calculating the amount of work accomplished 

 by a muscle, only the raising of the weight is taken into 

 consideration. When, however, the ordinary method 

 of irritating the muscle is applied, the weight which 

 is raised sinks back after each pulsation to its former 

 height. The muscular work accomplished at each pul- 

 sation is, therefore, cancelled. It is probably converted 

 into warmth. It is, however, possible to retain the 

 weight at the height to which it was raised by the muscle. 

 A. Fick' accomplished this very ingeniously by causing 

 the muscle to act on a light lever, which moves a wheel 

 each time it rises, but leaves the same wheel undis- 

 turbed when it again sinks. A thread, on which the 

 weight hangs, passes over the axis of the wheel. The 

 effect of this arrangement is that the muscle at each 

 pulsation turns the wheel slightly, and thus slowly 

 raises the weight. If the muscle is made to pulsate 

 frequently, the weight is raised somewhat higher each 



