64 PHYSIOLOGY OF Ml'SCLES AM) NFUVKS. 



we called the stage of latent irritation. When, how- 

 ever, weights are placed on the scale of the apparatus 

 (fig. 20), tin- r. suiting deflections of the magnetic needle 

 are different, and are greater in proportion as the weight- 

 applied is heavier. As the lever connected with the 

 muscle rests on, and is supported by, the plate below 

 it, the weights placed in the scale-plate cannot extend 

 the muscle ; they only increase the pressure of the 

 platinum point p on the underlying platinum plate. 

 Before the muscle can contract after irritation, the ten- 

 dency to contraction must be greater than this pressure, 

 or than the tension which is exercised from below bv 

 the weight on the lever. As the muscle strives to draw 

 up tin- lever, while the weight, on the other hand, draws 

 it downward, the greater force obtains the masterv. It 

 will be evident from what has been said that the muscle 

 acquires the force with which it strives to contract, not 

 suddenly, but very gradually. At the moment at which 

 this contracting force becomes slightly greater than the 

 weight applied, it is able to raise the lever, and in BO 

 doing to interrupt the current which determines the 

 time. If, in a serie< of consecutive experiments, hea\i.T 

 weights arc each time placed in the scale of the appa- 

 ratus, and if the deflections of the magnetic needle re- 

 sulting from this are measured, this determines the 

 periods in which tin- mu>cle attains a tendency to C"ii- 

 traetii.n equivalent to tl:c weight. \Ve \\ill call tin's 

 lon-e the energy of the muscle. So lon^ as the muscle 

 does not contract at all- that is, throughout the >ta^e 

 of latent irritation its energy = (). From the periods 

 which we find as the result of the application of in- 



creasing weights, it appears that this energy increases, 

 at first rapidly and then more >lowly, reaching itsmaxi- 



