in ELECTRICAL EXCITATION OF MUSCLE 215 



current must be considerably higher. Moreover, as we have seen, 

 the duration of current is of great moment ; at break excitation, 

 the anodic half of the muscle invariably begins to twitch before 

 the kathodic half, and the two curves seem in this way to be 

 relatively altered (24). 



Constant currents of very short duration (current impacts) 

 and single induction shocks are, as a rule, effective only at their 

 commencement, and not at the termination of the current. Chau- 

 veau observed in the muscles of living, warm-blooded animals, 

 that weak induction currents, and currents from a Leyden jar, 

 excite primarily in the kathodic region, and Engelmann emphasises 

 the entire correspondence of action between short battery currents 

 and single induction shocks, showing that an induction shock sent 

 through a long strip of rabbit's ureter at most discharges a wave 

 of contraction at the seat of the kathode, while it is only with 

 very great excitability, and currents of marked intensity, that 

 contraction sometimes appears to begin simultaneously at both 

 poles. It is not difficult to demonstrate the same effect in 

 striated muscle with similar excitation. If the curarised frog's 

 sartorius is again experimented on, and excited by a fresh 

 induction shock, the curve of twitch corresponding with the 

 kathodic half will always, after a brief latent period, rise earlier 

 from the abscissa, than that corresponding with the anodic half, 

 in the muscle stretched in the double myograph, and clamped in 

 the middle. 



With higher intensity of induction currents, however, the 

 anodic break stimulus also seems to become effective, which is 

 not surprising after Engelmann's experiments on the ureter. 

 Eegeczy (25) fixed the sartorius like Engelmann by clamping it 

 in the centre more or less firmly with ivory forceps, the other 

 end being immovably fixed by another forceps ; the lower end was 

 connected with the lever of the myograph. The lower electrode 

 was connected with the forceps fixed to the centre of the muscle, 

 the upper one was attached to the upper end of the muscle (cf. 

 Fig. 85). The direction of the induction current (coil at maximum 

 strength) can be changed by a reverser. IsTo difference was found in 

 the size of the latent period with ascending or descending currents, 

 as might have been expected from the experiments of v. Bezold, 

 Engelmann, and Biedermann, with battery currents. While with 

 weak induction currents the excitation starts from the kathode 



