108 S. WALTER RANSON 



a sharply-pointed triangular area, reaching a Uttle more than 

 halfway to the surface of the cord. It is rather sharply demar- 

 cated from the posterior funiculus, but spreads out into the lat- 

 eral funiculus, as indicated in the drawing. This lateral expan- 

 sion also presents a somewhat triangular form with the apex 

 pointing dorsally and separated from the apex of the main part 

 of the tract by the cerebellospinal fasciculus. It fades out ven- 

 trally into the funiculus proprius on the lateral surface of the 

 columna posterior. The entering dorsal root bundles run to- 

 ward the posterior horn upon the medial side of the tract. 



In the lumbar portions of the cord (fig. 6, seg. L. 5.) the columna 

 posterior reaches nearly to the surface of the cord and the tract 

 of Lissauer is compressed between it and the accumulation of 

 subpial neuroglia in the apex. The tract caps only the lateral 

 half of the substantia gelatinosa and is rather sharply delimited 

 toward the medial side. It is less sharply limited on the lateral 

 side and extends ventrally along the lateral surface of the col- 

 umna posterior as in the cervical and thoracic segments. The 

 entering radicles pass over the dorso-medial surface of the tract, 

 and cut off from the main part of the tract a few fibers which 

 form a small bundle near the surface of the fasciculus cuneatus. 



Structure 



The tract in the fifth cervical segment (figs. 7 and 8) contains 

 a relatively small number of medullated fibers of varying size. 

 Some are of medium caliber but the majority are very fine. 

 They are more widely separated than in the other fiber tracts 

 of the cord, and the tract as a whole is for this reason very lightly 

 stained in Pal-Weigert preparations. These fibers are for the 

 most part vertical in their course, appearing in the sections as 

 blue rings. There are also scattered oblique and horizontal 

 medullated fibers running through the tract in a dorso-ventral 

 direction. In almost every section through an entering radicle 

 one can trace a few fine medullated fibers (fig. 7, l.p.p.r.) out of 

 the radicle and into the tract of Lissauer. Many of these fibers 

 undoubtedly pass directly through the tract as the ol^lique or 



