ix ELECTRICAL EXCITATION OF NERVE 119 



current. " Ritter's tetanus " is a direct proof of its persistence 

 under certain conditions. 



The similarity of effect in closing or opening tetanus, and in 

 the true tetanus produced by discontinuous excitation, raises the 

 question whether here too there may not be fusion of single, 

 rapidly succeeding impacts of stimulation. In other words, does 

 the steady constant stimulus during closure, or after opening, 

 produce under the above conditions a discontinuous rhythmical 

 excitation of the nerve ; is the tetanus of closure and opening a 

 genuine tetanus or not ? We are familiar with the same difficulty 

 (supra) in the previous question of whether the tetanic contraction 

 of the muscle stimulated directly, or from its nerve, is really an 

 unbroken process, or whether discontinuous invisible changes are 

 masked by the apparent continuity. Ocular evidence is here 

 inconclusive. We may indeed reason with apparent probability 

 from the fact that every conceivable transition exists between 

 irregular tetani broken by single twitches (clonic) and a perfectly 

 steady (smooth) tetanus, and that these transitions must obviously 

 consist of so many more single twitches in the time-unit, in pro- 

 portion as they approximate to uninterrupted tetanus, that the 

 latter, too, consists of fused twitches : and the trembling which 

 concludes a long voluntary tetanus may equally be cited as 

 evidence of its discontinuity. This, however, is insufficient proof. 

 In addition to the form of the muscle-curve, the muscle-sound 

 and the electrical reaction of active muscle throw some light on 

 the nature of a persistent contraction. As regards the first, the 

 investigation of such a minute mass as a frog's muscle is obviously 

 very difficult (the experiment has not yet been tried for warm- 

 blooded muscle). And there has in fact been no result from the 

 various attempts at transmitting to the plate of a microphone, 

 or (according to Helmholtz's method) to consonant reeds, the 

 vibrations during the period in which a frog's muscle is in 

 closure-tetanus. 



On the other hand, experiments with the capillary electro- 

 meter upon the electrical reaction of muscle have yielded more 

 definite conclusions (v. Frey, 3), showing that closure-tetanus is 

 in fact derived from a succession of discontinuous rhythmical 

 impacts (10-15 per sec.) ; cnjo nerve like muscle is thrown, during 

 certain conditions, into persistent rhythmical excitation under the 

 action of current flowing at constant density. (The inadequacy 



