312 



MANUAL OF HISTOLOGY. 



FIG. 138. One-half transverse section of the 

 human medulla through the middle of the olives : 

 4, fourth ventricle ; 10, pneumogastric root ; 12, 

 hypoglossal root. 



little, except that in this space the root-fibres of the spinal 

 accessory seldom appear, although figured by most writers. 

 The region formerly occupied by the spinal accessory nucleus 

 contains a group of small cells which form part of the pneu- 

 mogastric nucleus. The fibres 

 between this nucleus and the 

 point of exit of the pneumo- 

 gastric root run so obliquely 

 upward, that no direct connec- 

 tion between them can be traced. 

 It is in sections at the mid- 

 dle of the olives that the pneu- 

 mogastric begins to appear dis- 

 tinctly. Most of its fibres seem 

 to be connected with a small 

 group of cells situated in the 

 gray matter, at the junction of 

 the funiculi graciles and the 

 restiform body. The gray mat- 

 ter of the restiform bodies is filled with small cells and con- 

 tains many fibres having a peripheral direction posterior to the 

 pneumogastric root the beginning of the auditory nucleus 

 and root. The olivary body here reaches its highest develop- 

 ment and greatest dimensions. 



Behind the olivary body is a small group' of cells, from 

 which scattered fibres pass backward and 

 inward toward the pneumogastric nucle- 

 us. But most of them are lost by as- 

 suming a longitudinal direction. This is 

 probably the lower facial nucleus, to be 

 described farther on. The arciform fibres 

 are chiefly confined to the surface of the 

 anterior pyramids and the olivary bod- 

 ies. The fibres of the raphe pursue, in 

 great part, an antero-posterior direction. 

 Sections through the medulla at the 

 upper part of the olivary bodies differ 

 little from the former sections. But a 

 small segment of the olivary bodies is present, and only a few 

 of the hypoglossal roots remain. (See Fig. 139.) External to the 

 remains of the hypoglossal nucleus is a nucleus of small cells 



FlO. 189. One half trans- 

 verse section of the human me- 

 dulla through the upper part of 

 the olives bringing the glosso- 

 pharyngeal tract (9.) and the 

 lower part of the acoustic nucleus 

 (80 into view. 



