WHITE MATTER OF MEDULLA. 301 



Spinal Tract of theTrigeminal Nerve. (Tractus spinalis nervi 

 trigemini, Figs. 92 and 96). It forms a narrow strip of the pos- 

 terior surface of the medulla, which is broadest near the restiform 

 body and tapers downward toward the spinal cord. It is composed 

 of the descending fibers from the sensory root of the trigeminal 

 nerve: the sensory fibers of this nerve on entering the pons divide 

 T-like, into an ascending and a descending branch, and the de- 

 scending branches form the spinal tract of the nerve, which for a 

 short distance is visible on the surface of the medulla. This 

 tract is continued through two segments in the spinal cord. The 

 nucleus of the spinal tract of the trigeminal nerve, over which it 

 runs and in which it terminates, is but the continuation of the gelat- 

 inous substance of the posterior columna of gray matter in the cord ; 

 in the upper medulla it is situated ventro-medial to the restiform 

 body. The nucleus produces a slight eminence below the level 

 of the clava, called the tuberculum cinereum. 



The cerebello-spinal tract (fasciculus cerebello-spinalis, Figs. 

 94 and 96) in the lower medulla crosses the posterior lateral 

 groove and the spinal tract of the fifth nerve, going from the lateral 

 column of the cord to the posterior area of the medulla; it then 

 ascends to form a considerable part of the restiform body. It 

 takes its origin from the nucleus dorsalis (Clarki) in the spinal 

 cord. It ends, very largely on the opposite side, in the cortex 

 of the superior cerebellar worm. The cerebello-spinal tract 

 (direct cerebellar tract) probably conducts common sensory im- 

 pulses received from viscera. They should be classed largely 

 under the muscular sense, as they seem to concern equilibrium 

 and orientation. They are sympathetic sensory. 



Restiform Body. (Corpus restiforme). In the upper medulla, 

 forming the lateral part of each posterior area, is a large rounded 

 bundle of fibers, called the restiform body (Figs. 92, 93 and 96). 

 It is the largest bundle in the medulla, and joins it to the cerebel- 

 lum. It is made up of the following: Ascending tracts (i) the 

 cerebello-spinal tract; (2) the external arcuate fibers, anterior 

 and posterior; and (3) the tract from the lateral nucleus of the 

 medulla to the cortex of the cerebellum. Descending tracts 

 (4) the cerebello-olivary fibers; and (5) a few axones of Purkin- 



