iv ELECTROMOTIVE ACTION IN MUSCLE 427 



the wound it disappears again. With Kiihne we must recognise 

 " that the nerves in situ are protected against the apparently 

 dangerous vicinity of the muscles between which they course, by 

 the characteristic properties of the latter, which forbid them 

 any activity relatively to each other beyond the hindering of 

 neutralisation of the myoelectric potential in the tract through 

 which the nerve passes " (which might perhaps be referred to the 

 principle of interference, or exclusion of the summated action of 

 the waves of variation). 



After Hering had determined that the muscle can be excited 

 by its own demarcation current, it was naturally presumed that it 

 must also be possible to produce secondary excitation from muscle 

 to muscle. In spite of many attempts the first experiments to 

 this end were totally ineffective, since neither on partial excita- 

 tion of a muscle were its fibres collectively, nor on total excitation 

 were the adjacent muscles, coexcited. Kiihne was the first who 

 succeeded in obtaining secondary (pre-systolic) excitation of the 

 frog's sartorius by the action current of the slowly beating tortoise 

 heart, which, as we have shown, is characterised by its secondary 

 inefficiency towards the nerves of the frog. This shows once more 

 the extent to which secondary excitation depends on the time-rela- 

 tions of the current of action : the more slowly reacting muscle 

 corresponds better with a slower wave of variation, while the 

 quickly reacting nerve is best excited by a rapid variation. Later 

 on Kiihne succeeded, under certain special conditions, in producing 

 secondary excitation from muscle to muscle on the skeletal muscle 

 of the frog also. 



While he never succeeded in bringing a sartorius into con- 

 traction by applying it to another directly, or indirectly, excited 

 muscle, without pressure, the effect never fails when the muscles 

 are partially pressed down upon one another (Kiihne, 57). Under 

 these conditions one muscle will produce secondary excitation in 

 a whole series of other muscles, brought together by the ends, 

 under pressure. Indirect excitation of the primary preparation 

 from the nerve is in such a case effectual, even when the secondary 

 excitation fails in a superposed nerve. This is especially true in 

 regard to clonic and tonic glycerin spasms, which fail to effect any 

 but very weak excitation in the secondary nerve-muscle prepara- 

 tion. This alters, however, as soon as the primary muscle is parti- 

 ally pressed down, when the secondary nerve, lying in the proximity 



