998 STRUCTURE OF THE BRAIN. [BOOK in. 



of the gracile and cuneate nuclei. To all parts of the cerebral 

 cortex, it appears to be joined by those conspicuous strands of the 

 pedal system, which, as we have seen, end in the pons, and there 

 make connections with the fibres of the middle peduncle. And 

 we may here perhaps remark that while this connection between 

 the cerebrum and cerebellum is wholly a crossed one, each cerebral 

 hemisphere being joined with the opposite half of the cerebellum, 

 the connections between the spinal cord and the cerebellum are 

 largely uncrossed ones, that by the cerebellar tract being wholly 

 uncrossed, and that with the posterior column by the relay of the 

 gracile and cuneate nuclei being in part uncrossed. 



Thus the cerebral cortex has a double hold, so to speak, on the 

 rest of the central nervous system first through the tegmental 

 system, and secondly through the cerebellar junction. But in 

 addition to this there is another tie between the cerebral cortex 

 and the whole length of the cerebro-spinal axis, or at least between 

 it and the whole series of motor mechanisms in succession from 

 the nucleus of the third nerve to the nucleus, if we may so call 

 it, of the anterior root of the coccygeal nerve, namely, the great 

 pyramidal tract, which thus appears as a something superadded 

 to all the rest of the central nervous system. 



When the cerebral hemispheres are removed this pyramidal 

 tract falls away as does also the pedal system leading from the 

 cerebrum to the pons, but there still remains the tegmental system 

 with its cerebellar and other adjuncts and this, as we shall see, 

 constitutes a nervous machinery, capable of carrying out exceed- 

 ingly complicated acts. 



