50 PHYSIOLOGY OF MUSCLES AND NERVES. 



tin- quiescent muscle when unweighted. If an experi- 

 ment i> successfully arranged so that an inactive muscle 



is not exlende.l by the Weight /,' by i';i-t eiiing t lie lat ter 

 ti tlie mu-c]e, but ininie(li;ite]y supporting it, so that 

 it does not extend (lie muscle and if the muscle is 

 then irritated, it is evident that the muscle is incapable 

 I' raising this weight from its support. Uy finding the 

 weight which is exactly sufficient i<> effect tliis, it is 

 evident that we shall find an expression for the magni- 

 tude of the energy with which the muscle strives to 

 pass from its natural into a contracted cnndilion. This 

 energy is called the force of the muscle. A method of 

 accurately determining this will presently lie explained. 



2. As far as it is possible to examine the matter, 

 the condition of muscles during their distinct pulsations 

 is exactly as in tetanus. All that has been said of the 

 height of elevation, and of the accomplishment of la- 

 bour dependent on this, and of the alteration in the 

 elasticity, is as true of distinct pulsations as of the 

 tetanic condition. J'ut it is \.T\ hard to observe the 

 alteration in form during the very short time \\hieh is 

 occupied by one of these pulsat ions. Means of drawing 

 very accurate conclusions even on this point have, how- 

 ever, been found, especially since Helmholtz turned his 

 attent ion to the matter, in 1S,~>2. 



Various methods are employed in experimental re- 

 search to measure very short period- of i imr accurately, 

 and to st i idy processes which occur even within tin- 

 shortest periods. ]S"ot only has the speed of the cannon- 

 ball during the various periods of its passage from the 

 mouth of the cannon to its arrival at its destination 

 been measured, but this has ;dso been done in (he, case 

 of the \e( shorter time occupied by the explosion of 



