222 



ELECTRO-PHYSIOLOGY 



CHAP. 



traversed in its entire length by the current. We saw that 

 excitation only remained unaltered when the effective elec- 

 trode was at the uninjured end of the muscle ; in other cases 

 it can be altered in a positive or negative sense when excitability 

 is locally increased or diminished. If the electrical excitation 

 of a muscle is once admitted to be a polar effect of current, it 

 cannot be doubted that the magnitude of both closing and 

 opening excitation must increase or diminish, as the excitability 



1 t 



T 







FIG. 89. Twitch curve of sartorius fixed from the centre in double myograph. , b, Normal ; 

 e, d, after treatment of one end with NaoCls (upper end of the muscle). Enormous increase 

 of the ascending closure twitch ; opening twitch with weak descending currents. 



of the contractile substance at the points where current enters 

 or leaves the muscle, increases or diminishes. Whether excita- 

 bility remains unaltered in all further sections of the muscle, or 

 whether it alters in a negative or positive direction, is undoubtedly 

 of great moment in the transmission of the excitatory process 

 from its origin, but has not the remotest influence upon the 

 intensity of the excitatory process discharged from kathode or 

 anode. We may conceive a muscle with parallel fibres of equal 

 diameter at both ends, having its cross - sections collectively 



