THE CENTRAL NERVOUS SYSTEM 



767 



both in the antero-lateral and posterior columns, and Sherrington 

 has shown (in the dog) that long proprio- spinal fibres passing 

 down in the lateral column connect the upper with the lower 

 parts of the cord (p. 804). 



The next question which arises is : How are the long tracts 

 connected below i.e., with the periphery and above i.e., with 

 the higher parts of the central nervous system ? The answer to 

 this question, partly derived from clinical records and partly 

 from experimental results, is in the case of some of the tracts 

 unexpectedly full and minute, though meagre in regard to others. 

 But to render it in- 

 telligible it is neces- 

 sary, first of all, to 

 describe briefly 



The Arrangement of 

 the Grey and White 

 Matter in the Upper 

 Portion of the Cere- 

 bro-spinal Axis. In 

 the medulla oblongata 

 the grey and white 

 matter of the spinal 

 cord is rearranged, 

 and, in addition, new 

 strands of fibres and 

 new nuclei of grey 

 substance make their 

 appearance. Of these 

 nuclei the most con- 

 spicuous is the den- 

 tate nucleus of the 

 inferior olive, which, 

 covered by a crust of 



white fibres, appears inferi or peduncle of the cerebellum; 4, clava ; 5, 

 as a projection on the superior peduncle crossing the inferior and passing 



to its internal side ; 7, 7, lateral sulcus ; 8, corpora 



quadrigemina. 



FIG. 318. MEDULLA OBLONGATA AND CEREBELLUM, 

 WITH FOURTH VENTRICLE (HIRSCHFELD). 



i, mesial groove of floor of ventricle running down 

 to the calamus scriptorius ; 2, striae acusticas ; 3, 



antero-lateral surface 

 of the medulla. In 

 front of the olive, be- 

 tween it and the continuation of the anterior median fissure, is 

 another projection, the pyramid, which looks like a prolongation 

 of the anterior column of the cord, but is made up of very 

 different constituents. Dorsal to the olive is the restiform body 

 or inferior peduncle of the cerebellum, and behind the restiform 

 body lie two thin columns, the funiculus cuneatus, which con- 

 tinues the postero-external column of the cord, and the funiculus 

 gracilis, which continues the postero-internal column. In these 

 funiculi are contained collections of small or medium-sized nerve- 

 cells termed respectively the nucleus cuneatus and the nucleus 

 gracilis. The rearrangement of the constituents of the cord is 

 due mainly to two causes : (i) The opening up of the central 

 canal to form the fourth ventricle, and the folding out, on either 

 side, of the grey matter which lies posterior to it in the cord ; 

 (2) the breaking up of the grey matter of the anterior horn by 



