CHAP, ii.] THE BRAIN. 951 



the cuueate nucleus it is Drought into connection with such parts 

 of the external posterior column as end in that nucleus, and thus 

 probably with other fibres of the posterior roots of the upper 

 spinal nerves. And if we admit that the cerebellar tract is 

 connected, by the relay of the vesicular cylinder or by other nerve 

 cells, with the rest of the posterior roots of the spinal nerves, we 

 may conclude that the restiform body is, by means of these relays, 

 a prominent continuation of all the spinal posterior roots. 



*The restiform body and so the cerebellum is also specially 

 connected with the olivary body of the opposite side ; for when in 

 young animals one side of the cerebellum is removed the olivary 

 body of the opposite side atrophies. The course of the fibres 

 maintaining this connection is not as yet accurately known, but 

 they probably pass from the olivary nucleus of one side through 

 the interolivary layer and so laterally through the reticular forma- 

 tion of the other side. Lastly we may add that a tract which is 

 sometimes included in the restiform body as its median or inner 

 division has quite a different origin from any of the above ; the 

 fibres which compose it come, as we shall see, from the auditory 

 nerve. 



The further connections of the bulb with the cerebrum it 

 will be best to leave until we come to deal with the structural 

 arrangement of the rest of the brain. 



Meanwhile enough has been said to shew that the bulb differs 

 very materially in structure from the spinal cord. The grey 

 matter of the bulb is far more complex in its nature than is that 

 of any part of the cord : and the arrangement of the several 

 strands and tracts of fibres is far more intricate. The structural 

 features on the whole perhaps suggest that the main functions of 

 the bulb are twofold ; on the one hand it seems fitted to serve as a 

 head centre governing the spinal cord, the various reins of which, 

 with the exceptions noted, it holds as it were in its hands ; on the 

 other hand it appears no less adapted to act as a middleman 

 between parts of the spinal cord below and various regions of the 

 brain above. As we shall see experiment and observation give 

 support to these suggestions. 



