and Plants to the Electrical Phenomena associated with it 53 



Up to this point the phenomena we have had under consideration 

 have been associated with the response of a muscle to a single instan- 

 taneous excitation, i.e., the monophasic variation and the momentary 

 contraction which it ushers in. We must now pass on to the considera- 

 tion of the electrical concomitants of those forms of contraction which 

 more obviously resemble the natural action of muscles. 



Physiologists have for half a cent my taught that natural muscular 

 action, whether reflex or voluntary, is made up of single contractions 

 of definite duration, such as those we have been considering, i.e., of a 

 rhythmical series of such contractions of definite frequency. This doc- 

 trine — that voluntary motion is a well organised system of twitches — is 

 now commonly expressed by calling it a tetanus, a word which was 

 some fifty years ago diverted from its medical signification to be 

 adopted as a technical term in physiology, but not precisely in its pre- 

 sent sense. What is now meant by it is that every contraction, how- 

 ever continuous it may appear to be, is in reality discontinuous. Tips 

 conclusion was arrived at by a method which, though sometimes of 

 great value to the physiologist, does not always lead to the discovery 

 of truth — the method which consists in first imitating a natural pro- 

 cess, and then mentally transferring the characteristics of the imitation 

 process to the natural process which it represents. In the present 

 instance the study of artificial tetanus has taught us a large proportion 

 of what we know as to the properties of muscle, but not much about 

 voluntary contraction. In assuming the identity of the latter with 

 experimental tetanus, physiologists have perhaps minimised certain 

 fundamental difficulties and assigned undue value to certain analogies. 



Of the difficulties, the most obvious one is that discontinuity could 

 not, if it existed, be of any advantage. For if we regard the muscular 

 system as the mere instrument of the central nervous system, and every 

 muscular fibre as the instrument of the motor cell which governs it, it 

 is difficult to see how subjecting that muscular fibre to a rhythm of its 

 -own could have any other effect than to interfere with its efficiency. 

 Of the analogies the chief are, first, that just as when you listen to a 

 muscle in artificial tetanus you hear a musical sound of which the 

 frequency of vibration corresponds to that of the stimuli, so a muscle 

 when contracting voluntarily gives out the quasi-musical sound, which 

 Wollaston compared to the rumble of wheels over pavement. The 

 other analogy relates to the reflex spasm of strychnine, 1 which is not 

 only rhythmical in itself, but is accompanied by a series of ' electrical 

 changes which are as rhythmical as if they were evoked by a series of 

 stimuli. The discussion of the muscle sound lies outside of our present 

 inquiry: the spasm of strychnine will be considered after we have 

 examined the electrical concomitants of artificial tetanus... ".. 



