84 LABORATORY OUTLINE OF NEUROLOGY 



tant descending tracts from the cerebral cortex (cortico-pon- 

 tile tracts). The fibers of the brachium pontis arise from 

 the nuclei of the pons, thus transmitting nervous impulses de- 

 rived from the cerebral cortex to the cortex of the opposite 

 cerebellar hemispheres. 



The superior peduncle (brachium conjunctivum) is the chief 

 efferent pathway from the cerebellum. These fibers arise 

 chiefly from the dentate nucleus (Section 98), enter the mid- 

 brain, and cross to the opposite side under the aqueduct of 

 Sylvius, after which they end in or near the red nucleus (nucleus 

 ruber) under the superior colliculus. The superior peduncle 

 also contains ascending fibers from the spinal cord (ventral 

 spino-cerebellar tract of Gowers). 



Between the superior peduncles is stretched a thin sheet of 

 nervous tissue, the anterior medullary velum. 



97. Inferior olives, pontile nuclei, arcuate nuclei, substantia 

 nigra. These gray centers of the brain stem are all function- 

 ally related with the cerebellum. All of these nuclei (except 

 perhaps the arcuate) send fibers to the cerebellar hemisphere of 

 the opposite side (see Strong ('15)) . Identify all of these nuclei 

 and enter them in the sketches. The cerebellar connections of 

 the inferior olive (olivo-cerebellar tract, see Herrick ('18), Figs. 

 72, 83 and 87) and of the pontile nuclei (brachium pontis, see 

 Herrick ('18), Fig. 87) should also be identified and indicated 

 on the sketches. The inferior olives and arcuate nuclei re- 

 ceive internal and external arcuate fibers from the sensory 

 nuclei of the oblongata. The inferior olive receives also a 

 strong tract from the thalamus (central tegmental tract) and a 

 smaller tract from the spinal cord (spino-olivary tract, see 

 Herrick ('18), Fig. 87). These cannot be easily distinguished 

 in the sections. Its chief discharge path is the olivo-cerebellar 

 tract and a smaller one (the olivo-spinal tract) discharges into 

 the spinal cord. 



98. Cerebellar nuclei. In addition to the superficial cortical 

 gray matter of the cerebellum there are several deep gray 

 masses. The largest of these is the dentate nucleus lying 

 within each cerebellar hemisphere, from whose neurons most 

 of the fibers of the superior cerebellar peduncle arise. Smaller 

 gray masses are found under the vermis near the roof of the 



