760 NEUROLOGY 





from cells in the motor area of the cerebral hemisphere of the same side, and 

 which, as they run downward in the medulla spinalis, cross in succession through 

 the anterior white commissure to the opposite side, where they end, either directly 

 or indirectly, by arborizing around the motor cells in the anterior column. A few 

 of its fibers are said to pass to the lateral column of the same side and to the 

 gray matter at the base of the posterior column. They conduct voluntary motor 

 impulses from the precentral gyrus to the motor centers of the cord. 



The vestibulospinal fasciculus, situated chiefly in the marginal part of the f uniculus 

 and mainly derived from the cells of Deiters' nucleus, of the same and the opposite 

 side, i. e., the chief terminal nucleus of the vestibular nerve. Fibers are also 

 contributed to this fasciculus from scattered cells of the articular formation of the 

 medulla oblongata, the pons and the mid-brain (tegmentum). The other terminal 

 nuclei of the vestibular nerve also contribute fibers. In the brain stem these fibers 

 form part of the median longitudinal bundle. The fasciculus can be traced to the 

 sacral region. Its terminals and collaterals end either directly or indirectly among 

 the motor cells of the anterior column. This fasciculus is probably concerned with 

 equilibratory reflexes. 



The tectospinal fasciculus, situated partly in the anterior and partly in the lateral 

 f uniculus, is mainly derived from the opposite superior colliculus of the mid-brain. 

 The fibers from the superior colliculus cross the median raphe in the fountain 

 decussation of Meynert and descend as the ventral longitudinal bundle in the 

 reticular formation of the brain-stem. Its collaterals and terminals end either 

 directly or indirectly among the motor cells of the anterior column of the same side. 

 Since the superior colliculus is an important visual reflex center, the tectospinal 

 fasciculus is probably concerned with visual reflexes. 



Ascending Fasciculi. The ventral spinothalamic fasciculus, situated in the 

 marginal part of the funiculus and intermingled more or less with the vestibulo- 

 spinal fasciculus, is derived from cells in the posterior column or intermediate gray 

 matter of the opposite side. Their axons cross in the anterior commissure. This 

 is a somewhat doubtful fasciculus and its fibers are supposed to end in the thalamus 

 and to conduct certain of the touch impulses. 



The remaining fibers of the anterior funiculus constitute what is termed the 

 anterior proper fasciculus (fasciculus anterior proprius; anterior basis bundle). It 

 consists of (a) longitudinal intersegmental fibers which arise from cells in the gray 

 substance, more especially from those of the medial group of the anterior column, 

 and, after a longer or shorter course, reenter the gray substance; (b) fibers which 

 cross in the anterior white commissure from the gray substance of the opposite 

 side. 



Fasciculi in the Lateral Funiculus. 1 . Descending Fasciculi. (a) The lateral 

 cerebrospinal fasciculus (fasciculus cerebrospinalis lateralis; crossed pyramidal 

 tract] extends throughout the entire length of the medulla spinalis, and on trans- 

 verse section appears as an oval area in front of the posterior column and medial 

 to the cerebellospinal. Its fibers arise from cells in the motor area of the cerebral 

 hemisphere of the opposite side. They pass downward in company with those 

 of the anterior cerebrospinal fasciculus through the same side of the brain as that 

 from which they originate, but they cross to the opposite side in the medulla oblon- 

 gata and descend in the lateral funiculus of the medulla spinalis. 



It is probable 1 that the fibers of the anterior and lateral cerebrospinal fasciculi 

 are not related in this direct manner with the cells of the anterior column, but ter- 

 minate by arborizing around the cells at the base of the posterior column and the 

 cells of Clarke's column, which in turn link them to the motor cells in the anterior 

 column, usually of several segments of the cord. In consequence of these interposed 



1 Schafer, Proc. Physiolog. Soc., 1899. 



