ME. J. L. CLAEKE OK THE INTIMATE STEUCTUEE OE THE BE AIK. 
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Of the Facial Nucleus and Nerve. 
(45) The peculiar course taken, by the roots of this nerve, at their origin from the 
floor of the fourth ventricle, as well as the intimate communications which they form 
with the roots of the abducens nerve, have rendered their examination so exceedingly 
perplexing, that although they have been carefully investigated by several eminent his- 
tologists, it is acknowledged that the question has never yet been satisfactorily settled. 
My own account of the course pursued by this nerve will be found to differ considerably 
from that of preceding anatomists, in consequence, I believe, of the different and more 
varied plan of investigation which I have adopted, and which has enabled me to deter- 
mine, with great accuracy, the points of peculiar difficulty. I shall first describe the 
minute structure of the facial nucleus. This nucleus occupies the greater portion of 
the convex longitudinal column which runs along the floor of the fourth ventricle on 
each side of the median furrow, and which is well known to anatomists as the “ fasciculus 
teres.” A transverse section of this column on the left side of the ventricle, and a little 
below the origin of the facial nerve, in Man, is accurately represented in fig. 50, Plate 
XIII. Like the rest of the ventricle, it is covered with a single stratum of columnar 
epithelium ( f Beneath the epithelium is a broad layer of grey substance, which is con- 
tinuous with that of the opposite side, beneath the median fissure. It consists of nuclei, 
cells, and fibres. The nuclei, for the most part, appear to belong to the connective tissue 
of the layer, and are very numerous. The cells, on the contrary, are sparingly scattered, 
and of small size. They are larger and more numerous along the under surface of the 
layer, and at its lateral part, where they are frequently collected into a small group ( g "). 
The fibres are of two kinds. Some of them, which are exceedingly fine, proceed from 
the tapering ends of the epithelial cells, and running through the layer in different 
directions, are connected in part with its nuclei. The others are connected with the 
nerve-cells and nerve-roots, and run both in a transverse and longitudinal direction. 
On the median side of the layer, at g" 1 , the transverse fibres (which appear to consist of 
those derived from both the epithelium and nerve-cells) are particularly numerous, and 
some of them decussate in front of the median furrow (h"), with their fellows of the 
opposite side. Sometimes at the side of the furrow there is a very distinct oval or fusi- 
form group of small cells, as shown on the right in the figure. 
(46) Beneath the lateral and middle portions of this superficial layer of grey substance, 
almost exactly the same time. My Essay on the Medulla Oblongata, in which the statement appears, was read 
before the Eoyal Society in June 1857, and published in Part I. of the Philosophical Transactions for 1858 ; 
and Schroder tan der Hole’s Essay on the Medulla Oblongata, in which the same fact is stated, was also 
published in 1858 (see his translator’s Preface). But there is some difference between Schroder van der Kolk’s 
account and my own. He considers that the whole of the grey tubercle in the upper part of the medulla 
consists of the descending root of the trigeminus, and that it differs in structure from the grey tubercle below 
the olivary bodies ; while I regard the grey tubercle throughout the medulla as the downward prolongation of 
the grey nucleus of the trigeminus, and the longitudinal bundles in front of the tubercle, as the downward 
prolongation of the fibres of the posterior root. 
MDCCCLXVIII. 2 T 
