78 ELECTRO-PHYSIOLOGY CHAP. 



time between stimulus and discharge of the muscle judiciously 

 determined, the twitch is invariably greater than under normal 

 conditions. The same also appears when the muscle is loaded 

 with increasing weights, and discharged at the same moment after 

 excitation. Place (32) found that on using a spring lever where 

 the resistance to be overcome, and consequently the tension 

 during the course of a contraction, increases steadily, the height 

 of the twitch increases also if the initial tension is raised from 

 to 25 gr. Tigers ted (26) subsequently observed an increment 

 in height of contraction with even higher initial tension, under 

 similar conditions ; and, lastly, the same relation is treated very 

 circumstantially by C. G. Santesson (32). 



From all these experiments we may conclude that within 

 certain limits the magnitude of contraction (height of twitch) in- 

 creases along with the initial tension, as well as with augmentation 

 of tension, during the period of contraction, to which it must be 

 added that this increment in height of twitch can neither be due 

 to the mechanical conditions of the experiment, nor to any 

 temporary alteration of excitability from the electrical stimulus, but 

 must be referred to a specific property of living muscle-substance. 

 As Tick expressed it, the muscle is not at a given moment of 

 the twitch invariably the same elastic body possessing a given 

 (uniform) tension in virtue of its actual length at the moment. 

 The cause of these manifestations can rightly be looked for in 

 nothing else than in a latent state of excitation, produced by, and 

 varying with, the mechanical conditions under which the twitch 

 is consummated. Schenk (33), indeed, states boldly that the 

 strong reaction by which the muscle always responds when its 

 contraction is in any way inhibited or even hindered, reacts upon 

 it again as a " stimulus," which may in its turn affect the pro- 

 cesses both of contraction, and, under some conditions, of 

 resolution of contraction also. As a rule the duration of the 

 contraction alters simultaneously with the height, on increasing 

 tension of the muscle ; on the other hand, the commencement 

 of shortening is not visibly affected. On raising the equi- 

 librated mass to be moved by the muscle to 200 grs., Tigerstedt 

 found that the latent period was very slightly lengthened in com- 

 parison with its proportions when only a light lever of hardly any 

 bulk was carried. 



The reaction thus described for the striated skeletal muscles of 



