396 PHYSIOLOGY CHAP. 



different methods : division of the root fibres within the cranium ; 

 section of the nerve directly it has left the jugular foramen ; 

 Bernard's method of tearing the nerve out. All the experiments 

 carried out with the first two methods constantly gave negative 

 results ; the normal movements of abduction and adduction of the 

 vocal cords, in both respiration and phonation, are in no way altered. 

 On the other hand, tearing the nerve out from the jugular foramen 

 always produced in rabbits immobility of the vocal cords in the 

 cadaveric position, on the side operated on ; this depends 011 the 

 intimate anatomical relations between the accessory and the lower 

 root filaments of the vagus, which are torn out with the accessory. 

 Grabower demonstrated that in rabbits, as in cats and dogs, the 

 motor and sensory innervation of the larynx is due to these root- 

 lets of the vagus, as iutracranial section of them produces motor 

 and sensory paralysis of the larynx on that side. When, on the 

 contrary, he destroyed the upper roots of the vagus, leaving the 

 lower roots intact, there was no disturbance of the normal functions 

 of the vocal cords. 



Grossmann, under Exner's direction, obtained practically the 

 same results as Grabower, and almost simultaneously. He 

 specially investigated the effects of intracranial electrical excita- 

 tion of the single rootlets, both of the vagus and the accessory, in 

 rabbit. Lake Grabower, he found that while stimulation of the 

 roots of the accessory produced no motor effect on the vocal cords, 

 that of the separate roots of the vagus produced strong adduction 

 or abduction of the corresponding vocal cord, or more or less 

 extensive contraction of almost all the laryngeal muscles. 



Since these experimental facts have overthrown the theory 

 which ascribed the innervation of the larynx to the internal 

 branch of the accessory, the question arises if the theory of the 

 origin of the inhibitory cardiac fibres of the vagus from the 

 accessory can be retained. As we have seen (Vol. I. p. 329), 

 Waller (1856) based this hypothesis on his observation that the 

 cardiac fibres of the vagus degenerated and the inhibitory effects 

 of stimulation ceased after extirpating the accessory. Schiff, 

 Heidenhain, Vulpian, and Jolyet confirmed his results. But after 

 Grabower had proved that some roots of the vagus are (constantly 

 in rabbit) torn away with the roots of the accessory by this 

 method of extirpation, both these observations lost their value as 

 evidence. On the other hand, Giannuzzi was unable, in rabbits 

 fourteen days after extirpation of the accessory, to demonstrate 

 complete loss of the inhibitory action of the vagus. While 

 Heidenhain, Vulpian, and Jolyet found acceleration of cardiac 

 rhythm the necessary effect of abolishing the tonic action of the 

 inhibitory fibres after destroying the accessory Schiff and Eckhard 

 obtained negative results. 



If the bulbar roots of the accessory therefore have no influence 



