THE DISSECTION OF THE BACK 



97 



surface of the posterior funiculus of the medulla spinalis. 

 It indicates the position of a septum which passes into the 

 funiculus from the deep surface of the pia mater and divides 

 it incompletely into two unequal strands. The groove is 

 termed the intermediate posterior sulcus. The strand on its 

 medial side is the fasciculus gracilis (Coil's), whilst the lateral 

 and larger strand receives the name of the fasciculus cuneatus 

 (Burdach's). 



The white matter of the medulla spinalis increases steadily 

 in quantity from below upwards. 



Fasciculus gracilis 



Postero-median septum *iflil Fasciculus cuneatus 



Postero-lateral sulcus 7~C ? n|ifHuPf v'* ^ 



Substantia gelatinosa 

 Rolandi 



Fasciculus cerebro- 

 spinalis lateralis 



Fasciculus spino- 

 cerebellaris posterior 



Fila of origin of 

 the accessory nerve 



Fasciculus cerebro- 

 spinalis anterior 



Antero-median fissure 



FIG. 28. Transverse section through the upper cervical part of the Medulla 

 Spinalis of a full-time Foetus, treated by the Pal-Weigert process. 



The fasciculi, gracilis and cuneatus, which form the posterior funiculus 

 of the medulla spinalis, are composed of fibres which enter the spinal medulla 

 as the fila of the posterior nerve-roots. In the lower portion of the medulla 

 spinalis the two fasciculi are not marked off from each other. 



In the lateral and anterior funiculi of the adult spinal medulla it is not 

 possible with the naked eye to distinguish the different strands of fibres of 

 which they consist, but the student should remember that such strands or 

 tracts are present. The three best-defined tracts in the antero-lateral part 

 of the spinal medulla are, (i)the fasciculus spino-cerebellaris (O.T. direct 

 cerebellar tract) ; (2) the fasciculus cerebro-spinalis lateralis (O.T. crossed 

 pyramidal tract) ; (3) the fasciculus cerebro-spinalis anterior (O.T. direct 

 pyramidal tract). 



The fasciculus spino-cerebellaris ascends to the cerebellum in thepostero- 

 lateral part of the lateral funiculus. Traced in the opposite direction, it 

 is found to disappear in the lower thoracic region of the medulla spinalis. 

 The fasciculus cerebro-spinalis lateralis occupies a larger district of the 

 medulla spinalis. It is placed in the lateral funiculus, anterior to the pos- 

 terior column of grey matter and immediately medial to the fasciculus spino- 

 cerebellaris. As the fasciculus spino-cerebellaris disappears in the lower 

 part of the medulla spinalis the fasciculus cerebro-spinalis lateralis comes 

 to the surface, and it can be traced as low as the fourth sacral nerve. The 

 fasciculus cercbro-spinalis anterior forms the narrow strip of the anterior 

 VOL. Ill 7 



