in ELECTRICAL EXCITATION OF MUSCLE 267 



plainly .than during the resting condition, and may even fail 

 altogether), polar inhibitory effects may be directly demonstrated, 

 and express themselves in the quelling, or diminution, of a pre- 

 viously existing state of excitation, and in a relaxation conditioned 

 by the same, which is in the first place local. The well-known 

 lencrtheninff, at closure of a homodromous current, of the muscle 



O O' 



in persistent opening contraction must be regarded as a kindred 

 phenomenon, preserving a distinctive character only in so far as 

 in this case there is inhibition of the state of excitation produced 

 by the after-effects of the previous current at the physiological 

 anode. Since a kathodic break inhibition may also be demon- 

 strated, at least incipiently, upon the veratrinised muscle, where 

 the curve in question drops suddenly, the hypothesis of two 

 inhibitory processes, antagonistic to the polar excitatory processes 

 (which do not, as a rule, find visible expression in striated skeletal 

 muscle, while in many smooth muscles, as also in cardiac muscle, 

 they are easily demonstrable during systolic contraction), would 

 appear to be perfectly justified. 



A few points still remain for consideration, i.e. certain 

 phenomena which may appear at closure during the electrical 

 excitation of striated muscle, and are obviously analogous to the 

 excitation phenomena appearing at the anode in many smooth 

 muscles. In both cases the effect is clue solely to the appearance 

 of secondary kathodic points. We have already seen that in the 

 longitudinally traversed sartorius (fixed by the middle clamp) 

 there is frequently, with strong ascending currents, a well- 

 marked persistent closure contraction in the anodic half 

 of the preparation also, which cannot be referred to an en- 

 croachment of the persistent K.C.C. 1 This is most plainly 

 seen with injury (death) of the kathodic end. In this case even 

 very strong, admortal currents (i.e. directed towards the demarca- 

 tion surface) fail to produce any trace of continuous contraction 

 at the limit of demarcation, although the muscle twitches sharply 

 upon closure of the circuit ; on the other hand, there is invari- 

 ably a continuous contraction at the anodic end of the muscle, 

 which increases directly with the strength of current. This 



1 A.C.C. = Anodic closure contraction. 

 A.O.C. = Anodic opening contraction. 

 K.C.C. = Kathodic closure contraction. 

 K.O.C. = Kathodic opening contraction. 



