ELECTROMOTIVE ACTION IN NERVE 



349 



tractile cylinder, its direction being towards the axis of the rami " 

 (du Bois-Eeymond, I.e. p. 555). To the end-surface of each hypo- 

 lemmal nerve-hook, du Bois-Eeymond ascribes the properties of an 

 artificial cross-section, pre-eminently that of negative potential in 

 relation to the " natural long section " of the terminal fibre 

 (Fig. 229). The negative variation of this pre-existing current 

 is the stimulus for the muscle- substance with which it is in 

 contact, and this implies the further, and highly improbable, 

 supposition that the muscle-substance is sensitive to such a weak 

 stimulus as the negative variation of the nerve current. Kiihne 

 (11, p. 90 ff.) instituted many experiments, as varied as possible, 

 with the view of discovering practical evidence for the modified 

 theory of discharge, or any parallel hypothesis, but with no 



result. What du Bois-Eeymond claims for a single primitive fibre 

 was not to be elicited on applying a vigorous frog's nerve, contain- 

 ing many hundred fibres, to a muscle under the most favourable 

 conditions, and then exciting it ; nor did the artificial transmission 

 of excitation from nerve to muscle come off any better with the 

 non-niedullated olfactorius of pike, in which the E.M.F. is much 

 higher (Kiihne's method). 



Kiihne himself, on the strength of his comprehensive re- 

 searches into the morphology of motor nerve- endings of verte- 

 brates, attempted subsequently to refer the innervation of the 

 muscle to electrical processes within the excited nerve ; but this 

 hypothesis went the way of all its predecessors, when confronted 

 with the growing knowledge of the motor nerve-endings in 

 invertebrates. Kiihne tried, by comparison of innumerable single 

 cases, to reduce the two main types of hypolemmal nerve-endings 

 in vertebrates, i.e. r pl&tzs (reptiles, birds, mammals, fishes), and 

 terminal fibres (arborisation of amphibia), to the simplest possible 



