190 ELECTRO-PHYSIOLOGY CHAP. 



this effect the analogue of that " final twitch," which, as we have 

 shown, sometimes appears at the end of tetanising excitation of 

 striated muscle with very frequent induced currents, just as the 

 " initial twitch " must be regarded, under the same conditions, as 

 analogous to the closure twitch on excitation with the constant 

 current. 



A fundamental distinction between the " twitches " produced 

 by single induction shocks and by the closure or opening of the 

 constant current is, as we have already pointed out, the more 

 extended curve (" tetanic character ") of the latter. The entire 

 process of shortening is prolonged in all its individual phases 

 (but especially in the stage of falling energy), in correspondence 



lull I i 1 j i J i < > A 1 A i i A 1 A i 1 I LJLJL i 



JLJULJLJL.i LJ-JLJLA. 



FIG. 80. Opening contraction (o) of adductor muscle of mollusc (Anodonta) after rhythmical 

 excitation with a strong constant current (10 Dan.). Incomplete tetanus during excitation. 

 Time-tracing in seconds. 



with the greater duration of the make or break excitation. The 

 relations of the latent period in both cases is a point of great 

 theoretical interest. We owe its thorough investigation to 

 Tigerstedt (2), v. Bezold (10) having previously ascertained that 

 the make twitch, with not unduly strong currents, has a shorter 

 latent period than the make induction twitch. The difference 

 according to Tigerstedt (in the non-curarised gastrocnemius) is on 

 an average O'OOS sec. We have invariably observed the same 

 results in experiments (to be described below) on the curarised 

 sartorius. In excitation with the constant current the magni- 

 tude of the latent period, as shown by v. Bezold, depends 

 essentially upon current intensity, the more so in proportion as 

 the current used for excitation is weaker. If the intensity of 



