CHAP, i.] THE SPINAL CORD. 855 



it, the " Wallerian method," has proved of great utility. Thus 

 in the vagus nerve which is composed not only of fibres which 

 spring from the real vagus root but also of fibres proceeding from 

 the spinal accessory roots, the two may be distinguished by 

 section of the vagus and spinal accessory roots respectively. 

 We shall presently see that this method may be applied to 

 the differentiation of tracts of fibres in the brain and spinal 

 cord. 



