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whole of the anterior cornu are gradually resolved or spread out 

 into a beautiful and complicated network, containing a multitude of 

 variously- shaped cells, which communicate and surround with their 

 processes the longitudinal bundles of the white columns enclosed in 

 the meshes. The post-pyramidal and restiform ganglia continue to 

 increase in size, as do also the terminal tufts of the posterior cornua, 

 which, like the former, are traversed by an extension of the network, 

 and interspersed with cells. At the lower extremity of the olivary 

 bodies, the decussation of the anterior pyramids, although still con- 

 siderable, is very much reduced ; for while its fibres derived from 

 the lateral columns have been gradually decreasing in number, those 

 which proceed from the posterior columns and posterior grey substance 

 have been increasing, though not in the same proportion. These 

 latter fibres may be traced backwards from the decussation chiefly to 

 the restiform body and its ganglion, in which they wander in various 

 directions, crossing each other, and becoming longitudinal. 



In front, and at the side of the central canal, a new group or co- 

 lumn of cells begins to make its appearance, the nucleus of the 

 hypoglossal nerve ; and behind and on each side of the canal appears 

 the nucleus of the spinal-accessory nerve, which is connected with its 

 fellow of the opposite side, at the bottom of the posterior fissure, by 

 a transverse band of fibres, the continuation of the posterior com- 

 missure of the medulla spiualis. Of the spinal-accessory nerve, 

 some of the upper roots proceed to their own nucleus, while others 

 bend forwards into the hypoglossal nucleus, and in part join its 

 fibres, to decussate through the raphe with those of the opposite 

 nerve. The vagus nerve arises from a continuation of the spinal- 

 accessory nucleus, and, on its way outwards, passes through the 

 terminal tufts of the posterior cornu, or the so-called gelatinous sub- 

 stance. The vagal and spinal-accessory vesicular nuclei or columns, 

 after appearing in the fourth ventricle, And diverging so as to expose 

 the hypoglossal nucleus, sink abruptly beneath a new mass of vesi- 

 cular substance which makes its appearance on each side of the ven- 

 tricle. This is the auditory ganglion. It commences by a point on 

 the outer side of the vagal nucleus, with which it is intimately con- 

 nected, and is developed from the inner part of the post-pyramidal 

 ganglion. Its cells are various in shape, and as they are developed 



