1912.] The Process of Excitation in Nerve and Muscle. 499 



condition reveals the fact that the conduction process is really no longer 

 normal. Boruttau and Frohlich* also opposed the usual interpretation. 

 They found that the longer the stretch of nerve narcotised the smaller was 

 the fall of excitability observed at the stage of narcosis in which the 

 conduction process first began to fail. It would seem probable from this 

 result that if we could use a sufficiently long nerve we should find that 

 even the smallest perceptible change of excitability brought with it a 

 measurable change in conductivity, and that our failure to recognise the 

 latter in the ordinary experiment lies merely in the fact that the propagated 

 disturbance, though diminished in the course of its propagation through 

 the narcotised region, is so little diminished that it still causes the muscle 

 to contract effectively. This possibility comes before us with even greater 

 force if we take into account the results of some work which Adrian has 

 recently carried out at Cambridge. He has been so kind as to allow me 

 to mention his results, which have not yet been published. He finds 

 evidence that a propagated disturbance passing down a locally narcotised 

 nerve will, if not too far diminished by its passage through the narcotised 

 region, actually recover in size again when it passes out into a normal 

 stretch of nerve beyond. This observation might appear to contradict the 

 experiments of Boruttau,f which showed that a propagated disturbance, 

 after emerging in such a way, was accompanied by an abnormally small 

 electric response, but in reality there is no contradiction, since Boruttau's 

 experiments did not exclude the possibility that the reduced response was 

 due to some fibres having failed to propagate any disturbance at all. If 

 this result of Adrian's proves to be well founded, it supplies an obvious 

 explanation of the failure of the muscle contraction to indicate small changes 

 in the size of the propagated disturbance transmitted through a narcotised 

 region, for the disturbance, by the time it reaches the muscle, may have 

 recovered its normal size again. 



It appears from this evidence that the dissociation of two processes by the 

 analytical method of Griinhagen is in all probability an illusion resting on 

 an inadequate method of determining changes in the size of the propagated 

 disturbance. The evidence is, however, still incomplete. We have no direct' 

 experimental proof that the degree of narcosis which first calls for a stronger 

 exciting current within the narcotised region does actually cause a diminu- 

 tion of the propagated disturbance as it passes through that region. Xor 

 will such evidence be obtained until we have an exact experimental method 

 of measuring small changes in that disturbance. As we have seen, the 



* Boruttau and Frohlich, lot: cit. 



t Boruttau, 1 Arch. f. d. ges. Physiol.,' vol. 65, p. 7. 



