

traverse the medulla, pass between the medial accessory and the inferior olivary 

 nuclei, (c) The dorsal accessory olivary nucleus is the smallest, and appears on 

 transverse section as a curved lamina behind the inferior olivary nucleus. 



6. The nucleus arcuatus is described below with the anterior external arcuate fibers. 



Inferior Peduncle (restiform body). The position of the inferior peduncles has 

 already been described (page 775). Each comprises: 



(1) Fibers from the dorsal spinocerebellar fasciculus, which ascends from the lateral 

 funiculus of the medulla spinalis. 



(2) The olivocerebellar fibers from the opposite olivary nucleus. 



(3) Internal arcuate fibers from the gracile and cuneate nuclei of the opposite side ; 

 these fibers form the deeper and larger part of the inferior peduncle. 



Cervical nerves 



Fid. 697. Nuclei of origin of cranial motor nerves schematically represented; lateral view. 



(4) The anterior external arcuate fibers vary as to their prominence in different cases: 

 in some they form an almost continuous layer covering the pyramid and olive, 

 while in others they are barely visible on the surface. They arise from the cells 

 of the gracile and cuneate nuclei, and passing forward through the formatio reticu- 

 laris, decussate in the middle line. Most of them reach the surface by way of the 

 anterior median fissure, and arch backward over the pyramid. Reinforced by 

 others which emerge between the pyramid and olive, they pass backward over 

 the olive and lateral district of the medulla oblongata, and enter the inferior 

 peduncle. They thus connect the cerebellum with the gracile and cuneate nuclei of 

 the opposite side. As the fibers arch across the pyramid, they enclose a small 

 nucleus which lies in front of and medial to the pyramid. This is named the nucleus 

 arcuatus, and is serially continuous above with the nuclei pontis in the pons; it 

 contains small fusiform cells, around which some of the arcuate fibers end, and 

 from which others arise. 



