BY A. JEFFERIS TURNER, M.D. 39 



intervenes between the stimulus and the contraction. Accurately 

 measured, this interval occupies about 1/lOOth of a second. 

 During this brief interval the electrical reaction of different parts 

 of the muscle undergoes a change. This change arises at the 

 point of stimulus, and travels as a wave along the whole length 

 of muscle, which, be it remembered, is still in an apparently 

 quiescent condition. Immediately or very soon after this 

 electrical wave has exhausted itself, the muscular contraction 

 begins. The conclusion can hardly be resisted that muscular 

 contraction is preceded as well as accompanied by physico- 

 chemical changes. The rate at which the electrical wave travels 

 has been measured ; in the frog it is about three metres ^lOft.) 

 per second. In warm-blooded animals it is probably somewhat 

 faster. Its wave-length in the frog is about 3 millimetres (one- 

 eighth of an inch). Surely these results point to the existence of 

 some very complex mechanism. But muscular contraction is a 

 vital act, performed by a living tissue. When we find that 

 similar electrical changes have been observed to accompany the 

 contractions of the leaves of the plant called Venus' Fly-trap, 

 the structure of which is as far removed as possible from 

 muscular tissue, we are, I think, justified in generalising, to the 

 effect that all movements of living matter, including those of the 

 amoeba, are due to physico-chemical changes, and depend on an 

 exceedingly complex mechanism. 



If we apply our electric shock, not to a muscle, but to a 

 nerve, no obvious result ensues, unless the nerve is attached to a 

 muscle. In that case the muscle contracts, showing that a 

 stimulus has been propagated along the nerve fibres. But 

 whethor a muscle be attached to the nerve or not, examination 

 by suitable apparatus will show that this propagation has been 

 accompanied by an electrical change precisely similar to that 

 which occurs in a muscle during the latent period, with the 

 exception that it has a greater wave-length, 18 millimetres 

 (three-quarters of an inch), and a considerably greater velocity. 

 This velocity in the frog is about 28 metres (92 feet) per 

 second, in man about 33 metres (107 feet) per second 

 (compared to the velocity of light, or electricity, or even of sound, 

 this is extremely slow). It can hardly be doubted that these 

 electrical changes in nerve fibres are due to some physico- 

 chemical mechanism, and that their velocity is fixed by this 



