24 Anatomy of the Nervous System 



in the gray matter of the dorsal column. Of those bearing 

 tactile impulses, some end very soon in the dorsal column, 

 but others extend for a longer or shorter distance up the 

 cord before terminating. Of the proprioceptive fibres, some 

 end after a short course in the cord while others run right 

 up to the lower end of the brain in company with some of 

 the exteroceptive fibres, which give the discriminative char- 

 acter to sensibility (Head). All these primary fibres running 

 along the spinal cord are grouped together in the dorsal 

 funiculus, which is thus made up largely of ascending pro- 

 prioceptive fibres mingled with some exteroceptive elements, 

 a number of shorter exteroceptive fibres, both ascending and 

 descending, and also certain axons which simply run from 

 one part of the cord to another — longitudinal association 

 fibres. At each level, the entering fibres take a position 

 lateral to those ascending from behind. Hence the fasciculus 

 gracilis contains the fibres which have come up from the more 

 posterior part of the cord, the fasciculus cuneatus those which 

 belong to the more anterior segments. 



The cells of the dorsal column of the gray matter which 

 receive impulses from these primary sensory fibres give rise 

 to secondary axons, many of which pass across the middle 

 line and take up a position in the lateral or ventral column 

 of white matter on the opposite side, there ascending to the 

 brain. These fibres are grouped in separate bundles according 

 to the type of sensory impulse which they carry, and all the 

 bundles together are known as the spinal lemnisctis. Others 

 of the secondary fibres enter the deeper part of the white 

 matter in any of the three columns on the same side and pass 

 up and down the cord for varying distances, finally ending 

 in connection with the cells of the cord itself and thus serving 

 as association paths. Yet other secondary axons arising in 

 the dorsal column go into the ventral column to connect 

 there with the motor cells giving rise to the ventral nerve 

 roots. These fibres are thus part of short reflex paths pro- 



