76 STUDIES IN ELECTRO-PHYSIOLOGY: 



conductors. Of what use is all this if nerve impulse is not 

 of an electrical nature ? 



Professor Rosenthal admits that the nerve substance 

 offers resistance to the passage of the nerve impulse. He 

 says : " It is probable that the propagation proceeds at 

 first at a greater and afterwards at a less speed," basing 

 this opinion upon Munk's experiments. " Its propagation 

 is gradually retarded. . . . From this it may be inferred that 

 a resistance to the transmission exists within the nerve, 

 and this gradually retards the rate of propagation." 



Reverting to the question of peripheric nerves, he goes 

 on to say that transmissions or irritation from one fibre 

 to another occur within the central organs of the nervous 

 system. " But in these cases it can be shown with great 

 probability that the fibres not only lie side by side, but 

 that they are in some way interconnected " (ganglion-cells 

 or sy nap tic junctions) " by their processes. In peripheric 

 nerve-fibres the irritation always remains isolated. Their 

 action is like that of electric wires enclosed in insulating 

 sheaths. One of these nerves may indeed be compared to 

 a bundle of telegraph wires, which are protected from 

 direct contact with each other by gutta-percha or by some 

 other substance. The comparison, however, is but super- 

 ficial. No electrically isolating membrane can really be 

 discovered in any part of the nerve-fibre, but all their parts 

 conduct electricity. When, as we shall find, electric 

 processes occur within the nerve, these standing in definite 

 relation to the activity of the nerves, we must assume that 

 isolation as it occurs in the nerves is not the same as in 

 telegraph wires. We cannot trace the matter here further, 

 but must accept the fact of isolated conduction as such, 

 reserving its explanation for a future occasion." 



Its explanation does not appear to me to present any 

 feature of difficulty. The endoneurium of a nerve-fibre 

 and I am adhering to the sciatic nerve may be said to 



