170 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



represent a cortico-spinal motor path in addition to that offered 

 by the pyramidal system. 



The vestibulo-spinal fibers, v.s., lie anterior to the preceding tract 

 in the anterolateral ground bundle; they may extend into the 

 anterior column as far as the direct pyramidal tract. These fibers 

 originate in the nucleus of Deiters and perhaps in the vestibular 

 nucleus of Bechterew in the pons. In the cord the fibers end around 

 cells in the anterior horn. Since the Deiters nucleus forms a termina- 

 tion for the sensory fibers of the vestibular branch of the eighth 

 cranial nerve, and since these fibers are believed to give us a sense 



of the position of the body 

 and to be concerned in the 

 reflex adjustment of the 

 muscles in the movements 

 to maintain equilibrium, 

 their connection in Deiters' s 

 nucleus with a spinal motor 

 path becomes very signifi- 

 cant as furnishing a reflex 

 arc through which sensory 

 impressions from the vestib- 

 ular apparatus in the ear 

 may automatically control 

 the musculature of the 

 body. The ventral longitu- 

 dinal bundle or fasciculus 

 sulcomarginalis (s.m., Fig. 

 75) lies along the border of 

 the anterior median fissure. 

 Its fibers are said to origi- 

 nate in the superior colliculi 

 of the corpora quadrigemina 

 and to terminate around 

 cells in the anterior horn, 

 constituting, therefore, a 

 second motor path between midbrain and cord. The anterior 

 marginal bundle, a.m., lies along the periphery of the anterior 

 columns, and is supposed to consist of fibers from the nucleus 

 fastigii of the cerebellum. Helweg's bundle is a small, triangular 

 area on the margin of the cord at the junction of the anterior and 

 lateral columns. It is conspicuous in the cervical region, and is said 

 to be connected with the olivary body, although little that is defi- 

 nite is known of its origin or termination. 



a.Tris. 



Fig. 75. Diagram indicating 



the location 

 of the" less well-known tracts of the cord: s., 

 Comma tract of Schultze; p.p., the prepyram- 

 idal tract (Monakow's bundle) ; v.s., region in 

 which are found the fibers of the vestibulo- 

 spinal tract; h., Helweg's bundle; a.m., an- 

 terior marginal bundle; s.m., ventral longi- 

 tudinal or sulcomarginal bundle; p. and p., the 

 direct and crossed pyramidal tracts; /. and g., 

 tracts of Flechsig and Gowers. 



