354 ELECTRO-PHYSIOLOGY CHAP. 



taneously closed for a short period. If this closure is effected 

 once at the moment of injury, and again after making the section, 

 the deflection in the latter case will be greater than in the former, 

 from which a " period of development " of the muscle current 

 may be concluded. Hermann carried out similar experiments 

 with the same results on muscles with parallel fibres (15). 



The correctness of these theoretical presumptions as to the 

 causes of animal (and vegetable) electrical currents, and the justi- 

 fication for rejecting every molecular hypothesis whatsoever, are 

 attested by the author's demonstration of the direct dependence 

 of the muscle current on local chemical changes in its substance. If 

 it is correct that in muscles and nerves, as in other animal and 

 vegetable tissues also, the electrical differences of potential which 

 may be demonstrated under certain conditions may always be 

 traced in the last resort to the different chemical reactions 

 between adjacent parts of the living substance, it must a priori 

 be granted as possible that the resulting electromotive action can 

 be neutralised again, in so far as there has not been such total 

 destruction as to prevent restoration of the normal activity of 

 the chemically altered substance. It is known that even excised 

 muscle possesses to a certain extent the capacity of readjusting 

 chemical changes in its substance, produced by certain excitants 

 (stimulants), e.g. " recovery " in " fatigued " muscle. We have 

 already drawn attention to the interest of the fact that, in- 

 dependent of previous excitation, a muscle may be thrown into 

 a state resembling fatigue by submitting it to the action of 

 certain chemical substances (" fatigue-substances "), after which, 

 by washing these out with an indifferent fluid, it can be restored 

 to its normal excitability (Ranke). It then becomes essential to 

 investigate how far electromotive action may result from the 

 contiguity of fibres which are chemically altered, but still capable 

 of recovery, and fibres that are in normal chemical activity. 

 Kanke's investigations of " chemical fatigue of muscle " by 

 salts of potash, or lactic acid, the striking effect of which 

 upon the phenomena of polar excitation by current has already 

 been discussed, appear to promise the best results. It is 

 found that after brief immersion of one end of a sartorius that 

 is free from current, in a dilute extract of muscle tissue, or 

 highly dilute solutions of potassium salts (KNO , IvH P0 4 , 

 KC1), it becomes strongly negative towards every other point of 



