312 THE RHOMBENCEPHALON. 



and, thence, through the dentate neurones by way of the brachium 

 conjunctivum cercbelli to the opposite red nucleus and thalamus. 

 The cortical fillet conducts all common sensory impulses from 

 the thalamus to the cerebral cortex. 



The nucleus olivaris inferior, the olivary nucleus of the medulla 

 (Figs. 92 and 94), is a sinuous, pouch-like collection of gray matter re- 

 sembling the nucleus dentatus of the cerebellum. It is situated 

 near the lateral surface of the medulla and is invested superficially 

 and deeply by fibers from the lateral fasciculus proprius. Its open 

 hilus looks medially and is filled with fibers, ihecerebello-olivary fibers, 

 which join it to the opposite hemisphere of the cerebellum. On 

 either side of the olivary nucleus is an accessory nucleus the 

 medial accessory, in the anterior area among the fibers of the 

 interolivary part of the medial fillet, and the dorsal accessory in. 

 the lateral area. The olivary nucleus, covered by fibers of the 

 lateral fasciculus proprius, forms the olive (oliva). The olive 

 shows the longitudinal extent of the nucleus and on section it is 

 seen to measure a quarter of an inch in depth. The olivary nucleus 

 is said to be a modern structure; it is found well developed only 

 in the higher mammals and does not appear in the human brain 

 until the sixth month. It probably contains both ascending and 

 descending neurones. Axones enter it from the nucleus funiculi 

 gracilis and nucleus funiculi cuneati and probably some of the 

 cerebello-olivary fibers are ascending in direction. It receives 

 two groups of descending fibers, viz.: (a) The descending cere- 

 bello-olivary fibers pass down from the cortex of the cerebellum 

 through the restiform body to the medulla, decussate and, entering 

 the hilus of the opposite nucleus, arborize and end about its cell- 

 bodies; and (b) the olivary fasciculus (central tract of the teg- 

 mentum), having descended from the lentiform nucleus through 

 the mid-brain and pons, fades away just dorsal to the olive and 

 probably ends hi it. Axones of the olivary nuclei of the medulla 

 have been traced by Kolliker and others down the lateral column 

 of the spinal cord. The triangular tract of Helwig is probably 

 composed of such fibers. It descends along the surface of the 

 cord lateral to the anterior roots of the spinal nerves and ends 

 in the gray matter of the cord. 



