COMMISSURAL FIBERS. 265 



and termination in the superior worm, forms its central part. 

 (2) The external arcuate fibers of the medulla (posterior and 

 anterior) form its free surface. They rise in the nucleus funic- 

 uli gracilis and nucleus funiculi cuneati and end in the vermis 

 superior, the posterior on the same and the anterior on the oppo- 

 site side. (3) A bundle from the lateral nucleus of the medulla 

 to the cerebellar cortex on the same side. (4) The internal arcu- 

 ate fibers to the opposite lower olive, the cerebello-olivary tract. 

 These constitute a large part of the deep area of the restiform 

 body and, with the acustico-cerebellar tract, make up all, or the 

 greater part, of the indirect motor path from the cerebellum to 

 the medulla. According to Cunningham the cerebello-olivary 

 are ascending fibers. 



There are probably a few axones of Purkinje's cells that run 

 down through the corpus restiforme and are continued without in- 

 terruption into the anterior descending cerebello-spinal tract of the 

 spinal cord; but surely the greater part of that tract is relayed in 

 the medulla and pons, chiefly in the nucleus of Deiters and in the 

 inferior olivary nucleus. (?) 



It should be noticed that the (posterior) cerebello-spinal fascic- 

 ulus, the external arcuate fibers and the anterior ascending cerebello- 

 spinal tract, with the tract from the lateral nucleus, are the in- com- 

 ing parts of the indirect sensory path, and that the brachium con- 

 junctivum is the out-going continuation of that path up to the red 

 nucleus and thalamus; and again, that the brachium pontis, the 

 acustico-cerebellar tract and the descending fibers of the resti- 

 form body constitute segments of the indirect motor path and 

 have to do with coordination and equilibrium. 



II. COMMISSURAL FIBERS. 



The cerebellar hemispheres are joined by transverse fibers, 

 of which there are two sets, namely: One near the anterior 

 end of the worm beneath the central lobe, and the other at the 

 posterior end of the worm. 



III. ASSOCIATION FIBERS. 



Limited areas of cerebellar cortex are richly associated together 

 as pointed out in the description of the cortical gray substance; 



