116 



ELECTRO-PHYSIOLOGY 



CHAP. 



second. The shortening of the apex-time is much more obvious 

 in incomplete tetanus, when the period of rising energy often 

 appears to be reduced to the third or fourth part of the time 

 which it takes in single twitches. 



Moreover, we learn from the relations of height in a contrac- 

 tion which is the sum of two simple twitches, that the theory, by 

 which the later of the two is regarded as a single contraction 

 upon a different abscissa, is not legitimate. Kronecker and Hall 



FIG. 48. a, Series of ascending ; 6, series of descending summated twitches. The place of the 

 second stimulus is the same in both cases, and only the first varies. The apex-height of the 

 summated twitches inclines towards the left. (v. Kries.) 



(3) found the height of "ascending" maximal contractions to be 

 greater at first than would correspond with Helmholtz's law, but 

 so much the smaller afterwards, according to the degree in which 

 the second contraction superposed itself behind the earliest 

 twitch. The greatest energy was developed by the second 

 impulse when it fell in the first -^ of the primary curve of 

 contraction. The curve does not then proceed as if the state of 

 contraction of the muscle at this moment were its point of rest, 

 the second twitch only being excited, but the impulse of the first 

 twitch is still effective. In the second and third - the second 



