550 TEXT-BOOK OF PHYSIOLOGY 



and functions. Some of the more important tracts are shown in Fig. 228. 

 They may be divided, however, into associative, ascending and descending 



tracts or fasciculi. 



i. The Associative Tracts. The associative tracts comprise the fibers 



heretofore spoken of as ground bundles, fundamental bundles, etc., 

 bundles of fibers which occupy those regions known as the ventral, 



lateral and dorsal root zones. Inasmuch as they are peculiar to the 



FIG. 228. DIAGRAM OF A TRANSVERSE SECTION OF THE SPINAL CORD SHOWING THE LOCA- 

 TION AND RELATION OF THE DIFFERENT FASCICULI. ASSOCIATIVE FASCICULI, i, Fasciculi 

 proprii, ventral, lateral and dorsal, i', the comma tract; i", the septo-marginal tract. THE 

 ASCENDING FASCICULI. 2, The dorso-internal (Goll); 3, the dorso-external (Burdach); 4^the 

 postero-marginal (Lissauer); 5, the dorsal spino-cerebellar (Flechsig); 6, the lateral spino- 

 cerebellar (Gower); 7, the lateral spino-thalamic; 8, the ventral spino-thalamic; 9, the spino- 

 tectal ; i o, the spino-oUvary. THE DESCENDING FASCICULI. 1 1 , The crossed-pyramidal tract ; 

 12, the direct pyramidal tract (Ttirck); 13, the rubro-spinal tract (Monakow's); 14, the vesti- 

 bulo- spinal tract. 



spinal cord they are termed fasciculi proprii of which there are dis- 

 tinguished a ventral, a lateral and a dorsal fasciculus proprius. These 

 fibers surround and for the most part lie close to the gray matter 

 throughout its entire extent. These fasciculi consist of fibers of 

 variable length which have their origin in the intrinsic nerve-cells of 

 the gray matter. From their origin the nerve processes pass outward 

 into the white matter on the same and the opposite sides, after which 

 they divide into two branches an ascending and a descending. After 

 a variable distance these branches re-enter the gray matter and 

 through their terminal branches come into relation with other in- 

 trinsic nerve-cells. By this means the segments of the spinal cord, 



