ELECTROTONUS 577 



As regards conductivity, it has been shown that excitation 

 travels best in the direction electrically uphill that is to say, 

 from a place of low to one of high electric potential. In 

 consequence of this fact a moderate excitation becomes 

 enhanced when travelling from the kathodic to the anodic 

 region. Conductivity is depressed, on the other hand, from 

 anode to kathode. An excitatory impulse is thus retarded 

 in travelling electrically down-hill. For these reasons, a 

 normal negative excitatory effect may, during transmission, 

 undergo either diminution of intensity, or actual reversal to 

 positive. 



With reference, again, to electrotonic variations of excita- 

 bility, we have seen that under feeble E.M.F. it is the ancde 

 that exalts, and the kathode that depresses. This conclusion 

 is obviously opposed to the generalisation known as Pfliiger's 

 Law, the extent of the applicability of which will be discussed 

 in detail in the following chapter. 



P P 



