MEDULLA OBLONGATA 427 



nervi trigemini} is shown in Fig. 438, and the tractus solitarius, containing 

 sensory fibers from the vagus and glossopharyngeus, is shown in the same 

 figure. In connection with these bundles of sensory fibers, there are 

 groups of nerve cells forming the nucleus of the tractus solitarius, and 

 nucleus of the spinal tract of the trigeminal nerve. These correspond with 

 the gracile and cuneate nuclei, and send fibers into the fillets. The fillets 

 continue through the pons and cerebral peduncles to the thalami, in 

 which they terminate. Nerve cells of the thalami convey the impulses 

 received onward to the hemispheres. Thus the sensory tract is com- 

 posed of three neurones, the first being in the ganglia of the sensory 

 nerves, outside of the central nervous system; the second begins in the 

 gracile and cuneate nuclei, or in the gray substance of the cord in case 

 the impulse travels by the spino-thalamic tract, or in the nuclei asso- 

 ciated with central tracts of the sensory cerebral nerves, and in all three 

 cases extends to the thalamus; the third begins in the thalamus and 

 extends to the cerebral cortex. 



CEREBELLUM. 



The medullated nerve fibers of the restiform bodies, brachia pontis, 

 and brachia conjunctiva come together to form the medulla of the cere- 

 bellum, and place the cerebellum in connection with spinal and cerebral 

 nerves and with the hemispheres. The medulla contains several paired 

 nuclei, the largest being the dentate nuclei, which have convoluted gray 

 capsules resembling those of the olivary nuclei (shown in Fig. 438). 



The restiform bodies include the fibers derived from the dorsal nuclei or columns 

 of Clarke in the spinal cord; these fibers ascend in the lateral funiculi, within which they 

 form the dorsal spino-cerebellar tract (of Flechsig). The restiform bodies contain also 

 fibers from certain cells in the gracile and cuneate nuclei, and many fibers from the 

 olivary nuclei, mostly of the opposite side. The brachia pontis contain fibers passing 

 to the cerebellum from the numerous nuclei pontis. The latter are in connection with 

 fibers descending from the hemispheres, thus forming cerebro- or cortico-cerebellar 

 tracts. Some fibers pass in the reverse direction. The brachia conjunctiva contain 

 fibers of the ventral spino-cerebellar tracts (of Cowers), which arise from central or 

 lateral cells in the gray substance of the cord, and pass through the lateral funiculi to 

 the brachia conjunctiva, through which they turn back to enter the cerebellum. The 

 main part of the brachia conjunctiva consists, however, of fibers passing outward 

 from the cerebellum and its dentate nucleus, to end, after decussating, in the red nuclei 

 of the mid-brain. Thence fibers pass on to the thalami and hemispheres, and also 

 downward to the medulla and spinal cord. 



The medulla of the cerebellum extends into the small peripheral lobules, 

 where it is covered by the cortical substance (Fig. 439). The latter 

 consists of three strata an inner granular stratum, which is rust-colored 

 in the fresh condition; a middle ganglionic stratum, composed of a single 

 row of large cell bodies ; and an outer gray stratum. 



