iv ELECTROMOTIVE ACTIOX IX MUSCLE 365 



a. 



persistently smaller, as in (l>, p,y), or whether this occurs spasmodic- 

 ally, so that the current may sink much deeper, and even below the 

 axis of the abscissa (which indicates reversed direction of current). 

 The effect upon the galvanometer is the same in both cases. In 

 the physiological rheoscope it is quite different. The form of the 

 curve (b, p, y] would never produce tetanus in the test-limb ; we 

 are reduced to the assumption that it is the jagged curve, though 

 with constant (unknown) depth of declinations, which really 

 occurs in tetanus " (du Bois - Keymond). In order to deal 

 fairly with the actual circumstances, it must also be noticed 

 that each individual elementary curve of variation fails, in con- 

 sequence of the after-effect, to reach the height of the original 

 ordinate, so that the base-points 

 of the single curves form a 

 descending staircase, as in 

 Fig. 113. Supported by these 

 facts and hypotheses, du Bois- 

 Eeymond believed himself justi- 

 fied in propounding a general 

 theory of Matteucci's second- 

 ary contraction, representing it 

 simply, i.e. as the physiological 

 effect of the negative variation 

 of the muscle current present 



in evei'V single twitch, and Only FlG - H3.-Xegative variation in tetanus. 



* (Hermann.) 



marked by the sluggishness of 



the magnet. (It is to be noted that the modern galvanometers 

 with light, aperiodic magnets present no such difficulty, and 

 the demonstration is as certain as in the physiological rheo- 

 scope). According to this view, du Bois held it to be a 

 necessary condition for the appearance of the secondary twitch, 

 that the nerve of the secondary preparation should occupy a 

 definite position upon the primary muscle. According to his 

 first results, the secondary contraction only appears regularly 

 " when the nerve closes the circuit between the two dissimilar 

 surfaces of the muscle (longitudinal and transverse section)." 

 Matteucci had meantime found the appearance of the secondary 

 contraction to be fairly independent of the position of the nerve 

 upon the primary preparation, and had even placed it so that 

 it formed a loop round the twitching muscle. It is, in fact, very 



