PROFESSOR AT KONIGSBERG 65 



experiment you are on is wonderfully lucky do oblige me by 

 keeping to it ; we could work into each other's hands, and get 

 something out of it.' 



It was not surprising that this brief communication from 

 Helmholtz should again arouse questioning and contradiction 

 on the part of the older physiologists and physicists. Johannes 

 M tiller had expressly stated six years before that we never 

 should be able to determine the rate of the nervous impulse, 

 since we had no means of experimenting over enormous 

 distances, by which the velocity of light, in this respect analo- 

 gous with the activity of nerve, had been calculated. He 

 held that the time occupied by the passage of a sensation 

 from periphery to brain and cord, and the efferent reflex that 

 produces a contraction, is too infinitesimal to be measured. 

 And, indeed, so long as the nervous impulse was referred by 

 physiologists to the diffusion of an imponderable agent, or to 

 a psychical principle, it necessarily appeared incredible that 

 the velocity of this current could be measurable within the 

 short compass of the animal body. Du Bois' work had, how- 

 ever, made it more than probable to Helmholtz that the propa- 

 gation of excitation in nerve is essentially conditioned by 

 altered arrangement of the molecules, whence he conjectured 

 that rate of propagation is a measurable, and even a moderate 

 magnitude, since it is a case of molecular action in ponder- 

 able bodies. 



These investigations all fell into place in the chain of 

 Helmholtz's thoughts and opinions, which were directed, to 

 the exclusion of any metaphysical speculation, towards the 

 discovery of facts alone. It is interesting to find that while 

 the opponents of 'nature-philosophy' had set themselves , 

 against the Law of the Conservation of Energy, because they 

 saw in it merely a philosophical play of ideas with no strong 

 scientific basis, the next, strictly physico-physiological, work 

 of Helmholtz provoked doubt and remonstrance not only from 

 the physiologists, but from the philosophers also, as they were 

 unable to admit a time-interval between the idea and the con- 

 comitant physiological action. 



In order to explain this antagonism it is only necessary to 

 remember the views that prevailed at that time in regard to the 

 connexion of the sciences, more particularly of physiology 





