THE MAMMALIAN NERVOUS SYSTEM 91 



the restiform body receives on its ventral side a large tract from 

 the olive, but this cannot be dissected at this time without 

 destroying the intervening structures ventrally of the restiform 

 body. At the level of the olive the restiform body turns slightly 

 ventralward, crossing superficially the anterior end of the tuber- 

 culum cinereum (tubercle of Rolando or spinal V tract), and 

 then passes backward ventrally of the most superficial fibers 

 of the tuberculum cinereum. Dissect out this part of the 

 restiform body and follow it backward into the spinal cord, 

 where it will be seen to form the dorsal spino-cerebellar tract 

 of Flechsig (Section 96). Summarizing the corpus restiforme, 

 this inferior peduncle of the cerebellum is composed chiefly of 

 ascending fibers from the great proprioceptive sensory centers 

 of the spinal cord, the inferior olive, and the vestibular root 

 and nucleus of the VIII nerve. 



104. Brachium pontis. — At the base of the cerebellum locate 

 the fibers of the brachium pontis, which form the most lateral 

 fibers of the cerebellar peduncles. Beginning at the most 

 ventral part of the pons, gradually tease off the pons fibers, 

 stripping them upward a few at a time into the cortex of the 

 cerebellar hemisphere, and note the way in which those from 

 the anterior (rostral) border of the pons pass obliquely back- 

 ward ventrally of those from the posterior (caudal) border. 

 Trace these two layers out separately and- determine their 

 distribution in the cerebellar hemisphere. In the dissection of 

 the pons be careful to preserve the fibers of the V- nerve. The 

 brachium pontis fibers as a whole form two thick layers, the 

 fibrse superficiales and the fibrse profundae, separated by the 

 longitudinal fibers of the pons (pyramidal tract, etc.). The two 

 layers of pons fibers above mentioned belong to the super- 

 ficial system. Strip off the remaining superficial pons fibers 

 until the longitudinally directed pyramidal tracts are exposed. 

 The fibers of the brachium pontis will be now seen to inter- 

 digitate with the fascicles of longitudinal fibers. These fasciculi 

 can be followed forward into the midbrain where they form the 

 most ventral fibers of the pedunculus cerebri. Expose these 

 longitudinally directed fibers for a short distance forward 

 (rostrad) and backward (caudad) of the pons. Do not com- 

 pletely dissect them, but leave them in place for future reference. 



