Roth, Spinal Accessory Nerve. 



491 



ory descended to the level of the sixth nerve, the increase did 

 not occur until the seventh nerve. These relations may be 

 expressed in tabular form thus : 



Level of lowest root of spinal 

 accessory. 



Anterior root in which increase 

 of small fibers occurs. 



Left side 

 Right side 



5th nerve 

 6th nerve 



6th nerve 

 7th nerve 



These observations in the cat are by no means so conclu- 

 sive as those made upon the rat, but nevertheless they harmo- 

 nize admirably with them, and the case of the fifth cat is espe- 

 cially interesting as showing that the correlation of the white 

 rami fibers with the origin of the lowest root of the spinal 

 accessory nerve occurs even in cases of individual variation. 



Addendum. 



From the above observations there appears to be, in both 

 the rat and the cat, a sudden increase in the number of white 

 rami fibers in the ramus communicans of the nerve which imme- 

 diately succeeds the last root of the spinal accessory nerve, and 

 the conditions demanded by Gaskell's supposition are fulfilled. 

 It does not, however, necessarily follow that the significance 

 which Gaskell assigns to the spinal accessory is the correct 

 one. It may be true that the cranial lateral motor roots are 

 serially homologous with the visceral motor roots, i.e., the 

 white rami fibers of the cord ; indeed, there is much to recom- 

 mend such a view. But that the spinal accessory, or to be 

 more precise, the cervical portion of that nerve, actually repre- 

 sents the white rami fibers of the upper cervical spinal nerves 

 is more than doubtful. 



It is becoming more and more apparent that the classifica- 

 tion of the spinal accessory as a distinct unit in the series of 

 cranial nerves is erroneous ; it is rather merely a portion of the 

 vagus, whose continuation down the spinal cord is no more re- 

 markable than the downward extension of the spinal tract of 

 the trigeminus. It is true that the fibers of the latter nerve 

 pursue their downward course in the substance of the central 



