8o4 MAN 



Gow), the spinothalamic (Spt), rubrospinal (Rst) and Deiterso-spinal 

 (DT), tracts together w ith the usual juxtagriseal intersegmental association 

 fibers. In the ventrohiteral region is the spino-oiivary tract of Helweg (Hel). 



LEVEL OF THE CAUDAL EXTREMITY OF THE 

 DORSAL SENSORY NUCLEI (FIG. 343) 



At this level the changes are those incident to the appearance ni the 

 dorsal sensory field of the nuclei of Goll ( NG) and of Burdach (NB). 

 The [nramidal decussation is still in process at this level as indicated bj- 

 the marked dellection of the ventromedian sulcus. The reticular lormation 

 (Ref ) has increased in size as compared with the lower level, so much so 

 that the cephalic remnant of the \entral gra\' column ( Ven ) is now connected 

 by many griseal bridges with the central gray matter (Cen). The latter 

 structure has migrated somewhat dorsally in the general movement which 

 takes place in preparation tor the opening oi the fourth \ entricle. The dorsal 

 sensory columns of Goll and Burdach still show their exact demarcation b\ 

 means of the dorsal paramedian sulcus. The column ol Goll is about one-third 

 the size of the column of Burdach. In both of these columns there now 

 appears the corresponding nuclear structure. The nucleus of Burdach is a 

 l^rotrusion of the central gra\- matter into the in\esting medullary substance 

 of Burdach's column. The nucleus of Goll occupies a more independent 

 position almost entiri'l\' surrouiuk'd b\ medullary substance. The substantia 

 gelatinosa of Rolando ( N R) shows some increase in dimensions as compared 

 with the last level, and the descendingtrigemiiial tract ( Trd) is also obviously 

 larger. The central gra\ matter (Cen) is roughly triangular in shape with 

 its base directed toward the dorsal aspect of the stt'in. Its triangular form is 

 in part accounted for by tlu' decussating fibers of the pyramidal system 

 (Py.\). The cervix of the dorsal gray column is rc|)ri-s<.'nted only by a few 

 gray bridges connecting tlu' substantia gelatinosa trigt'inini with the central 



