268 



ELECTRO-PHYSIOLOGY 



CHAP. 



effect is unmistakable to the unaided eye, or with a magnifying 

 lens, but with the graphic method many additional details can be 

 detected. If a sartorius (stretched in the double myograph, 

 killed at the pelvic end, and clamped in the middle) is excited 

 by currents of increasing strength (4-8 Dan., with rheochord), 

 the first effect produced will be only the normal reaction of 

 muscle injured at one end, as described already. Excitation 

 with a descending current is followed by a pronounced make 

 twitch (fairly symmetrical in both halves of the muscle), with a 

 subsequent persistent contraction, which appears in the kathodic 

 half only. The closure of the ascending current is at first with- 

 out any effect, even at such a strength of current as would in 

 the normal muscle provoke maximal closure contractions under 

 the same conditions. Beyond a certain limit of intensity, how- 

 ever, the ascending (admortal) current once more begins to excite 

 at closure, often indeed before an effective break excitation 

 appears with the same direction of current under conditions 

 favourable to its development, because the current is of greater 

 density at its exit from the small end of the muscle. 



The make excita- 

 tion always expresses 

 itself at first as a 

 pronounced twitch on 

 the anodic side with- 

 out any conspicuous 

 persistent contrac- 

 tion. With increased 

 strength of current, 

 however, this appears 

 also, exclusively in the 

 anodic half of the 

 muscle ; the kathodic 

 half relaxes completely after the make twitch has subsided (Fig. 94). 

 At a certain strength of current the latter nearly always 

 overtops the twitch at closure of the descending (" abniortal ") 

 current. With increasing current intensity, the persistent A.C.C. 

 increases rapidly at the lower end of the muscle, and in its turn 

 soon exceeds the persistent K.C.C. of the descending current in 

 magnitude and extension (Fig. 94). 



In addition to this, the gradual swelling of the persistent 



FIG. 94. Sartorius fixed at the middle, killed at the pelvic 

 end(O). (8 Dan.) Persistent anodic closure contraction. 

 After a pause of twelve minutes the effect of the de- 

 scending make excitation (at 6) had decreased consider- 

 ably, while the ascending excitation remained uniform. 



