THE SPINAL CORD AND CEREBELLUM 105 



nection with the cortical cells, are very important 



sensory channels. 



Those fibres which pass to the motor cells of the The sen- 

 sory and 

 ventral horn and those which cross the opposite side motor 



of the cord seem by reason of their connections to be in the 

 of a co-ordinating nature. They bring, so far as one 

 is able to judge, one part of the nervous system into 

 relation with another. What, then, is the function of 

 the remaining fibres of the posterior root, both coarse 

 and fine ? It will be remembered that the anterior 

 root was said to be composed of motor, vaso-motor, 

 secretory, and perhaps secreto- motor (to the muscularis 

 mucosae) fibres ; and one is the less inclined to look 

 for a reduplication of any of these in the posterior 

 root, since it is the sensory root. Motion and 

 sensation are most closely allied, although distinct ; 

 and probably in all organisms the former is the 

 consequence, and, one might almost say, the continua- 

 tion, of the latter. They represent, as it were, the 

 wave and counterwave in a vibratory movement. 

 The whole architecture of the spinal cord, the division 

 of its gray matter into what one may look on as a 

 motor and a sensory horn, the distribution of its 

 white matter and of the nerve-roots in a corresponding 

 manner — all this seems to be based on the fact of the 

 anatomical difference between sensation and motion. 



But if for this reason one should put aside all motor The fine 



, . , • 1 , fibres of 



impulses, excluding at the same time any which might thepos- 

 be termed purely co-ordinating, and those which are roots. 

 sensory in the ordinary sense, and are believed by 



