148 



THE NERVOUS SYSTEM 



funda). Those of the superficial group lie ventral to the longitudinal fasciculi; 

 while the deep transverse bundles interlace with the longitudinal ones or lie 

 dorsal to them. The majority of the fibrae pontis cross the median plane. These 

 are joined by some uncrossed fibers and gathered together on either side of the 

 pons to form a compact and massive strand, known as the brachium pontis or 

 middle cerebellar peduncle, which curves dorsally to enter the white center of 

 the cerebellum (Figs. 88, 108). 



^X * >v 



V Cerebral cortex, 



-y Corticobulbar tract 

 - * Corticospinal tract 



Temporopontine tract 

 Frontopontine tract 



- Pons 



- Cerebellum 



"' Nuclei pontis 



x Brachium pontis 



Lateral corticospinal tract 

 Ventral corticospinal tract 



Fig. 106. Diagram of the cortico-ponto-cerebellar pathway and the corticospinal and cortico- 



bulbar tracts. 



Along the rostral border of the pons and brachium pontis one or two fiber bundles are 

 sometimes found which run an isolated course to the cerebellum. These are known as the 

 fila later alia pontis or Icenia pontis (Fig. 88). According to Horsley (1906) the constituent 

 fibers arise from a ganglion situated caudal to the interpeduncular ganglion, decussate at once, 

 and end in the cerebellum in the neighborhood of the dentate nucleus. Perhaps they rep- 

 resent slightly displaced fibrae pontis. Some of the transverse fibers on reaching the median 

 plane bend at right angles and run as fibrse rectae toward the pars dorsalis pontis (Fig. 108). 

 According to Edinger (1911) these belong in part at least to the tractus cerebellotegmentalis 

 pontis, which arises in the nuclei of the cerebellum and runs through the brachium pontis 

 to end in the reticular formation of the opposite side (Fig. 153). Cajal (1909) is doubtful 

 about the existence of such efferent fibers from the cerebellum in the brachium pontis. 



The nuclei pontis, which are continuous with the arcuate nuclei of the 

 medulla oblongata, contain stellate nerve-cells of varying size, the axons of 



