INTERNAL BRANCH OF THE SPINAi ACCESSORY. 173 



eral times performed it with entire success, and verified, in 

 every regard, the facts observed by Bernard. Within the 

 last year, the excellent assistant to the chair of Physiology 

 at the Bellevue Hospital Medical College, Dr. C. F. Koberts, 

 has succeeded in extirpating these nerves for class-demonstra- 

 tions. The operation is generally most successful in cats, 

 though Bernard has succeeded frequently in other animals. 



When one spinal accessory is extirpated, the vocal sounds 

 are hoarse and unnatural. When both nerves are torn out, 

 in addition to the disturbance of deglutition and the partial 

 paralysis of the sterno-mastoid and trapezius muscles, the 

 voice becomes extinct. Animals operated upon in this way 

 move the jaws and make evident efforts to cry, but no vocal 

 sound is emitted. This condition is very striking ; and in- 

 asmuch as Bernard has kept animals, with both nerves ex- 

 tirpated, for months, the question of the function of these 

 nerves in phonation may now be regarded as definitively 

 settled. 



It remains now to consider the experimental facts with 

 regard to the influence of the different filaments of origin 

 of the spinal accessory on the voice. These are simple, and 

 entirely conclusive ; and they are due exclusively to the re- 

 searches of Bernard. This experimenter found that division 

 of the roots of origin from the spinal cord not only did not 

 affect the voice, but sometimes seemed to render it clearer ; 

 but that division of the roots of origin from the medulla ob- 

 longata abolished the voice, though the inferior roots were 

 intact. 1 



It is not necessary to discuss the action of the muscles 

 of the larnyx in phonation, as this subject has already been 

 considered in full in another volume. 3 The beautiful experi- 



nerve. Soon there is a cracking sensation conveyed to the hand as the roots 

 give way, and the nerve may then be drawn out entire. With care, either the 

 filaments of origin from the medulla or those from the cord may be extirpated 

 alone. (BERNARD, op. cit., p. 736 ; and, Lemons sur la physiologic et la pathologic 

 du sysleme nerveux, Paris, 1858, tome ii., p. 296.) 



1 Op. cit., p. 735. s See vol. i., Voice and Speech, p. 490, et seq. 



