THE SPINAL CORD AS A CONDUCTING PATH 



617 



on which they have arisen, but finally cross the median line by way of the sensory 

 decussation of the medulla. It is also to be noted that the fibers which 

 have their origin at a low level, are gradually pushed toward the median fissure 

 by those fibers which enter at higher levels, and naturally, as this displacement 

 affects the exogenous fibers only, the upper thoracic and cervical segments of the 

 fasciculus gracilis gradually assume the character of the conducting path for the 

 root fibers of the lumbar and sacral regions. 



cerebral 



cortex 



trkjeminal lemniscus 

 sKin 



medial lemniscus 



nucleus of dorsal 

 / / / funiculus 



spinal lemniscus 



ventral pyramidal 

 tract 



lateral pyramidal tract 

 spinal (jancjlion 

 sKin 



muscle 



FIG. 306. DIAGRAM OF THE CHIEF CONNECTIONS BETWEEN THE SPINAL CORD AND THE 



CEREBRAL CORTEX. 



The spinal lemniscus complex carries the ascending exteroceptive systems (touch, 

 temperature, and pain) ; the dorsal funiculus and medial lemniscus complex carry 

 chiefly ascending proprioceptive impulses (a nerve of muscle sense is the only member 

 of this group included in the drawing). The diagram also shows the sensory path from 

 the skin of the head to the cerebral cortex through the V cranial nerve (trigeminus) 

 and the trigeminal lemniscus. The pyramidal tract (tractus corticospinalis) is the 

 common descending motor path for both exteroceptive and proprioceptive nervous 

 impulses from the cerebral cortex. (Herrick.) 



(b) The direct or spinocerebellar tract (Flechsig's) is one of the two best known 

 tracts in the lateral funiculus. As its fibers arise in the cells of Clark's column, 

 they are endogenous in character, and serve for the inward conduction of those 

 impulses which have attained the aforesaid cells by way of certain fibers of the 

 posterior root. While most of them enter the inferior peduncle of the cerebellum 

 and terminate in the posterior and median areas of the vermiform lobe, some also 



