PROJECTION FIBERS. 263 



I. PROJECTION FIBERS. 



All fibers that leave the cerebellum, or enter it, do so through 

 the brachia, the restiform bodies and the superior medullary 

 velum, hence these are composed of projection fibers. At a higher 

 level the projection fibers are contained in the corpus medullare. 



Brachium Conjunctivum (Figs. 44, 77 and 78). The brach- 

 ium conjunctivum (superior peduncle) is the innermost of the three, 

 at its origin in the anterior cerebellar notch; external to it, in the 

 notch, are the restiform body and the brachium pontis; and, in 

 the angle between the brachium conjunctivum and the restiform 

 body, is the vestibular nucleus of Bechterew (the upper part of 

 Deiters's nucleus). The brachium conjunctivum is joined to 

 its fellow of the opposite side by the superior medullary velum 

 (velum medullare superius). Two bundles of fibers run through- 

 out the brachium conjunctivum. They are afferent and efferent. 

 First, the fibers to the cerebrum, which comprise nearly the whole 

 brachium, are axones of cell-bodies situated in the nucleus denta- 

 tus. This group of fibers partially buries itself in the dorsal area 

 of the pons, then penetrates the mid-brain and decussates ventral 

 to the inferior quadrigeminal colliculi. It ends largely in the 

 opposite red nucleus, but partly in the thalamus. It constitutes 

 one segment of the indirect sensory path. In the red nucleus 

 this path is relayed to the thalamus and to the cortical fillet, or 

 the relay is directly into the cortical fillet. It is probable that a 

 few fibers of this brachium terminate in the nuclei of the third 

 and fourth, and perhaps the sixth cerebral nerves. The second 

 group of fibers rises in the opposite red nucleus, pursues a reverse 

 course and ends in the nucleus dentatus. A few fibers from 

 Bechterew's nucleus are found in the cerebellar end of the bra- 

 chium conjunctivum and the fila lateralia pontis traverses the 

 same part of it. Although the greater number of these fibers 

 in the conjoined brachia decussate in the tegmentum, a few run 

 to the red nucleus and thalamus of the same side; while the fila 

 lateralia cross in the pons from the opposite pontine nucleus and 

 the commissural fibers between Bechterew's vestibular nuclei 

 leave the brachium and cross through the superior velum in the 

 isthmus. The superior medullary velum (Fig. 65) arches over 



