352 THE SPINAL CORD. 



posterior roots, running from the posterior-lateral sulcus to their 

 destination in the gray matter, and (c) axones of intrinsic neu- 

 rones connecting posterior with anterior parts of the crescent. 



The longitudinal fibers comprise most of the white matter 

 in the cord, forming the funiculus anterior, funiculus lateralis 

 and funiculus posterior (Fig. 101). These three great columns 

 occupy the anterior, lateral and posterior areas of the cord. They 

 are disposed around the gray crescent in bundles or tracts. The 

 tracts which make up the funiculi are not visible to the naked 

 eye, nor under the microscope in a healthy adult cord; they have 

 been located by embryological, experimental and pathological 

 investigations. The longitudinal fibers rise in the brain, hi the 

 spinal cord and in the spinal ganglia; some run upward and others 

 downward, constituting the tracts of the cord. Thus the tracts 

 are characterized as ascending, descending and mixed tracts. 



Ascending Tracts: (i) Ascending anterior cerebello-spinal 

 and spino-thalamic tract. (2) Cerebello-spinal tract (direct cere- 

 bellar) with the spino-vestibular tract. (3) Marginal tract (of 

 Lissauer). (4) Fasciculus cuneatus. (5) Fasciculus gracilis. (6) 

 Ciaglinski's long sensory tract, hi the posterior commissure. 



Descending Tracts: (i) Anterior (direct) pyramidal tract, 

 including the anterior longitudinal bundle. (2) Lateral (crossed) 

 pyramidal tract. (3) Descending anterior cerebello-spinal tract, 

 including Helwig's tract. (4) Rubro-spinal tract (Pawlow). (5) 

 Descending postero-medial tract, called at different levels the 

 comma, oval, and septo-marginal tract. (6) Descending postero- 

 lateral tract. 



Mixed, Ascending and Descending Tracts: (i) The ante- 

 rior fasciculus proprius, includiug the medial longitudinal bundle. 

 (2) Lateral fasciculus proprius. (3) The posterior fasciculus 

 proprius, composed of the cornu-commissural tract, the septal 

 bandalette of Hoche, and possibly a part of the comma, oval, 

 septo-marginal and the descending postero-lateral tract (Cun- 

 ningham). 



The methods of locating tracts of fibers may be summarized 

 briefly, as follows: 



The embryological method was first employed successfully 



