364 



ANATOMY OF THE CENTHAL NERVOUS SYSTEM. 



connected only by a thin "neck" with its dorsal extremity, here greatly 

 thickened by substantia gelatinosa, forming the "head of the dorsal horn." 



Through the substantia, gelatinosa pass numerous fine fibrils, which are partly 

 posterior root-fibers. Another portion of them comes from a greater distance, namely 

 from the Gasserian ganglion. The cells of this ganglion emit peripherally the nervus 

 trigeminus, and centrally the trigeminal root. A part of these latter fibers turn 

 downivard, and from them pass continuously fine fibrils to the end-nucleus of the 

 trigeminus: a column of gelatinous substance, ^\■hich is demonstrable from the pons 

 down to the substantia gelatinosa of the upper cervical cord. The crescentic trans- 

 verse section of the tractus spinalis of the fifth nerve lies in the cervical cord in close 



Cga 



Fig. 231. — Cross-section of the oblongata through the pyramidal decussa- 

 tion. Fpy, Pyramidal tract. Cga, Anterior horn. Fa', Eemnant of anterior 

 column. IsUj, Nucleus funiculi gracilis, g, Substantia gelatinosa. XI, Nervus 

 aeeessorius. (After Henle.) 



proximity to the substantia gelatinosa, as in the oblongata and the pons. It can be 

 seen in all the sections hereafter represented (Figs. 232 and 238, for example). It 

 has, until now, been called the ascending root of the fifth nerve (see also Fig. 251). 



Further one finds the lateral horns here well developed. From cells 

 lying at their bases and higher up, appearing on the lateral edge of the an- 

 terior horn, comes the nervus aeeessorius Willisii. Its root-fibers which 



