592 HANDBOOK OF PHYSIOLOGY. 



side a small mass of gray matter, external arcuate nucleus; laterally 

 another mass of the same material, the representative of the lateral nu- 

 cleus 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 fibres of the 

 spinal cord upward into the bulb and beyond : 



The crossed and direct pyramidal tracts have already been described. 

 Nothing definite is known of the antero-lateral descending tracts. The 

 cerebellar tracts pass laterally into the restiform bodies and go to the 



Fig. 362. Section of the medulla oblongata at about the middle of the olivary body. /. I. a. , 

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

 nerve emerging from the surface ; at 6, it is seen coursing between the pyramid and the olivary 

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

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

 ascending root of the fifth nerve, a, V. : X, bundle of vaguS root emerging; f.r. , formatio retic- 

 ularis; c.r., corpus restiform, beginning to be formed, chiefly by arciform fibres, superficial 

 and deep; n.c., nucleus cimeatus; n.g., nucleus gracilis ; t, attachment of the ligula; f.s., funi- 

 culus 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 olivae. (Modified 

 from Schwalbe.) 



cerebellum. The antero-lateral ascending tracts appear to have the 

 same destination and pass directly or indirectly into the cerebellum. 

 The fibres of the postero-median and postero-external columns end in 

 the nuclei of the fasciculus gracilis and cuneatus respectively, either in 

 or about the cells contained in those nuclei ; at any rate, ascending de- 

 generation of these columns cannot be traced above these nuclei. 



The rest of the fibres of the cord appear to end in the reticular for- 

 mation of the bulb. The bundle of fibres constituting the ascending 

 root of the 5th nerve appears to correspond with the tract of Lissauer. 



Connections of the bulb with the cerebrum and cerebellum, In addition 



