ii CHANGE OF FORM IN MUSCLE DURING ACTIVITY 75 



perceptibly extended before it begins to shorten (31). This 

 effect fails when the recording lever is connected with the lower 

 end of the muscle, i.e. under normal conditions of recording a 

 muscular contraction. The shortening of the entire muscle is 

 not therefore preceded by any lengthening (extension). Each 

 individual muscle element is, however, in the first place extended 

 by the excitation, or contraction, of a distant spot, for the loaded 

 muscle exerts a greater traction on its point of dependence so 

 long as it pulls up its load in contracting, than during rest (Gad). 

 It is therefore clear that under these conditions the mechanical 

 latent period of the whole muscle must be longer than the 

 mechanical latent period of the muscle element, and that accord- 

 ingly the shortest latent period observed in the whole muscle 

 must approximate most nearly to the true value of that of the 

 muscle element. In order to cut out this delay in the latent 

 period as far as possible, each point of the entire muscle would 

 have to be simultaneously excited, which is not the case in any 

 form of electrical excitation. Even where current passes through 

 the entire muscle, the excitation, as will be shown, proceeds only 

 from given points of the area stimulated. Here, again, the 

 mechanical latent period represents only the upper limit of the 

 true latency, since the energy (mechanical yield of work) of the 

 muscle must already have exceeded a certain output, in order to 

 produce a visible movement of the lever. 



Tigerstedt (I.e.), from a great number of experiments, carried 

 out under most varied conditions, determined the following 

 values for the mechanical latent period in the frog's gastroc- 

 nernius : 



According to this table the mechanical latency would be 

 from 0-004 to 0*006 sec.; in most cases (41 / ) it} was 0'005 

 sec. The mechanical latent period of the muscle elements 

 could certainly not exceed 0'004 sec., but is probably much 

 smaller, since it is certain that within the time usually reckoned 



