iv ELECTROMOTIVE ACTION IN MUSCLE 383 



must be the less negative, the nearer they lie to the end not 

 excited. Hermann gave direct proof of this by leading off 

 from a number of loops of thread, placed round a regular 

 muscle with parallel fibres ; one end of the muscle was tetanised, 

 and the E.M.F. of the action current determined between each 

 pair of contacts. He found it " approximately proportional to 

 the relative distance of the loops and quite independent of their 

 position." " Each point traversed by the excitation is thus, 

 during tetanus, the seat of electromotive force, homodromous 

 with the wave of excitation." And thus it appears that the 

 " negative variation " in its original manifestation is no more 

 than a special case of the action current in tetanus, in which 

 the reciprocal phases ensue on leading off from an artificial 

 transverse section. 



Since under normal conditions the muscle is always excited 

 indirectly, i.e. from the nerve, a special interest attaches to the 

 investigation of the action current in uninjured muscle with this 

 kind of excitation ; the more so as all the earlier experiments on 

 the negative variation were made, from motives of convenience, 

 with what is intrinsically the least suitable object the frog's 

 gastrocnemius tetanised through its nerve. The same uninjured 

 muscle was also the subject of the first series of exact analytical 

 experiments made on the action current, with indirect excitation, 

 and led off from the two tendinous ends by Sigmund Mayer (28) 

 under Bernstein's direction, and with his rheotoine. The compli- 

 cated manifestations observed (accounted for by every possible 

 interpretation and explanation) first became intelligible when 

 Hermann, in 1877, began to investigate the action current of regu- 

 larly constructed parallel-fibred muscles, with indirect excitation. 

 With our present knowledge of the relations between nerve and 

 muscle it is legitimate to assume that the excitation is discharged 

 at a definite point in every muscle-fibre, on stimulating the nerve 

 fibre belonging to it, i.e. at the nerve end-plate, which is situated 

 between the contractile substance of which it is the continuation, 

 and the nerve-fibre of which it is the conducting organ. We shall 

 presently have to examine the histological and physiological relations 

 between nerve and muscle in detail ; for the moment it is enough 

 to say that it has been ascertained that the nerve-fibre is connected 

 with only a limited tract of the muscle-fibre or fibres belonging- 

 ing to it, which by no means prevents the same muscle-fibre from 



