422 SPECIAL HISTOLOGY. 



entry of the roots of the nerves into the grey substance could 

 not escape notice. Since the junction of the radical fibres with 

 the anterior, posterior, and lateral columns, can be so well and so 

 directly observed, the relation in question would necessarily be 

 evident also; and yet in the course of my perfectly unpre- 

 judiced observations, I have never seen anything of the kind. 

 Nothing, therefore, remains but to assume, that the great 

 majority of the peripheral nerves really have a cerebral 

 origin. Whether they all originate in the brain (where, we 

 shall afterwards see) or in part, though, from my observations, 

 but to a small extent, from the cord, cannot be determined, 

 any more than the question can be decided, whether the white 

 substance of the cord, besides the fibres derived from the 

 peripheral nerves, also contains others passing from the brain 

 to the cord.] 



The medulla oblongata and pons Varolii belong to the most 

 complex parts of the central nervous system, containing white 

 and grey substance, intermixed in very various modes. The 

 white substance is, in part, a continuation of that of the cord, in 

 part distinct from it, and is disposed in the following manner: 

 the anterior columns of the spinal cord diverge from each 

 other at the commencement of the medulla oblongata, allowing 

 the decussating fibres of the corpora pyramidalia to appear. 

 As they proceed, a smaller division joins the pyramids, forming 

 their outer part, whilst the principal portion surrounding the 

 olivary bodies, internally and externally, whence they are also 

 termed the olivary columns, passes laterally, and then, divided 

 into two bundles, proceeds above the second transverse layer 

 of fibres, through the pons. One of these divisions constitutes 

 the fillet, (laqueus,) which continued above the crura cerebelli ad 

 cerebrum, enters the posterior corpora quadrigemina, joining, 

 within them, the corresponding division of the opposite side. 

 The second division, or bundle, lies externally and inferiorly to 

 the crura cerebelli, and enters the tegmentum of the cerebral 

 peduncle. Besides this, the olivary columns, corresponding to 

 the anterior columns of the cord, also, as it seems, give off 

 fibres to the pedunculus cerebelli. The lateral columns of the 

 spinal cord divide, on reaching the medulla oblongata, into three 



