GREY AND WHITE MATTER IN CEREBRO-SPINAL AXIS 869 



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. 908). 



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

 nected 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 intelligible it is necessary, first of all, to describe briefly 



SECTION IV. ARRANGEMENT OF GREY AND WHITE MATTER 

 IN THE UPPER PORTION OF THE CEREBRO-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 conspicuous is the 

 dentate nucleus of the in- 

 ferior olive, whi ch , covered 

 by a crust of white fibres, 

 appears as a projection on j 

 the antero -lateral surface 

 of the medulla. In front 

 of the olive, between it 

 and the continuation of 

 the anterior median fis- 

 sure, is another projec- 

 tion, the pyramid, which 

 looks like a prolongation 

 of the anterior column of 

 the cord, but is made up 

 of very different consti- 

 tuents. Dorsal to the 

 olive is the restiform body 

 or inferior peduncle of the 

 cerebellum, and behind 

 the restiform body lie two Fig . 347 Medulla Oblongata and Cerebellum, with 

 thin columns, the fumcu- Fourth Ventricle (Hirschfeld). i, mesial groove 

 his cuneatus, which con- of floor of ventricle running down to the calamus 

 tinues the postero-exter- scriptorius; 2, striae acusticae; 3, inferior peduncle 

 nal column of the cord, of the cerebellum; 4, clava; 5, superior peduncle 

 and thefuniculus gracilis, crossing the inferior and passing to its internal 

 which continues the pos- side ; 7, 7. lateral sulcus; 8, corpora quadrigemina. 

 tero-internal column. In 



these f uniculi 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 strands of fibres as they sweep through it from 

 the lateral pyramidal tract to take up a position in the pyramid of the 

 opposite side (decussation of the pyramids), and a little higher up by 



