TRACTS THROUGH THE MEDULLA 539 



matter, one more ventral to the other, called accessory olives, external and 

 internal, and on the surface of the anterior pyramid on either side a small 

 mass of gray matter, external arcuate nucleus; laterally another mass of the 

 same material, the representative of the lateral nucleus of the cord, is seen, viz., 

 the antero-lateral nucleus, which gives origin to the spinal accessory nerve. 



It will be necessary to follow as shortly as possible the fibers of the spinal 

 cord upward into the bulb and beyond. 



Tracts Through the Medulla. The crossed and direct pyramidal tracts 

 have already been described. Nothing definite is known of the antero-lateral 

 descending tracts. The direct cerebellar tracts pass laterally into the restiform 



n.am 



FIG. 379. Section of the Medulla Oblongata at about the Middle of the Olivary Body, f.l.a., 

 Anterior "median fissure; n.ar., nucleus arciformis; p., pyramid; XII., bundle of hypoglossal 

 nerve emerging from the surface; at b, it is seen coursing between the pyramid and the olivary 

 nucleus, o.; f.a.e., external aroiform fibers; n.l., nucleus lateralis; a., arciform fibers passing 

 toward restiform body, partly through the substantia gelatinosa, g., partly superficial to the 

 ascending root of the fifth nerve, a. I'.; X., bundle of vagus root emerging; f.r., formatio retic- 

 ularis; c.r., corpus restiforme, beginning to be formed, chiefly by arciform fibers, superficial and 

 deep; n.c., nucleus cuneatus; n.g., nucleus gracilis; t, attachment of the ligula; f.s., funiculus 

 solitarius; n.X., n.X.', two parts of the vagus nucleus; n.XIL, hypoglossal nucleus; n.t., nucleus 

 of the funiculus teres; n.am., nucleus ambiguus; r., raphe; A., continuation of the anterior column 

 of cord; o', o", accessory olivary nucleus; P.O., pedunculus olivas. (Modified from Schwalbe.) 



bodies and go to the cerebellum. The antero-lateral ascending tracts (Gow- 

 ers) appear to have the same destination, but pass indirectly into the cere- 

 bellum by way of the superior medullary velum; some of the fibers probably 

 pass upward to higher centers. The fibers of the postero-median and postero- 

 external columns of Goll and Burdach, of the cord, end in the nuclei of the 

 fasciculus gracilis and cuneatus respectively ; at any rate, ascending degenera- 

 tion of these columns cannot be traced above these nuclei. The rest of the 

 fibers of the cord appear to end in the reticular formation of the bulb. 



Connections of the Bulb with the Cerebrum and Cerebellum. The 



