272 
ME. J. L. CLAKKE ON THE INTIMATE STRUCTURE OE THE BRAIN. 
mass several bundles of fibres with intervening layers of grey substance ascend longitu- 
dinally through the grey network with which they constitute the outer nucleus of the 
auditory nerve ( c' o, fig. 23.). The inner nucleus («, fig. 24) of the auditory nerve, 
although marked off from g by the dotted line to indicate its limits, is really directly 
continuous with it ; neither can any alteration of structure be discovered, as the one 
passes into the other. 
(13) I have been thus exact and particular in following out the gradual transitions 
and morphological changes which take place in ascending the medulla, not only on 
account of their extreme importance directly and indirectly in both a pathological and 
physiological point of view, but also on account of the necessity of understanding exactly 
the structure, connexions, and relations of the various elements of this part of the 
medulla, in order to interpret correctly the morphological and histological relations of 
the parts which are situated higher up. And indeed I believe that these changes which 
I have thus described, and which have cost me no small amount of thought and labour 
to follow out and confirm, will be the means of correcting many errors, and of leading 
to a more exact knowledge of other parts of the brain. 
(14) But before I proceed to these parts it will be necessary to describe some new 
and important facts which I have recently ascertained with regard to the structure of 
the medulla oblongata. 
In my former memoir on this subject, I gave the following composition of the anterior 
pyramids, according to my observations at the time : — 
1. Decussating fibres of the anterior commissure, continuous with that of the spinal 
cord. 
2. Decussating fibres from the opposite lateral columns, constituting their chief bulk. 
3. Decussating fibres from, the posterior grey substance. 
4. Non-decussating fibres of the anterior columns, forming a small part on their outer 
side. 
Now subsequent observations, while they have confirmed the truth of these statements, 
have enabled me to make some important additions. I had already shown that the 
decussating fibres from the posterior grey substance proceed out of the post-pyramidal 
nucleus, the restiform nucleus, and the posterior horn, near its extremity, as represented 
in figs. 3 & 4, Plate VIII. I have since ascertained, by means of longitudinal sections 
made at appropriate angles, that some of the decussating fibres of the anterior pyramids, 
which appear only to cross the antero-lateral grey substance, in their course from the 
opposite lateral column, do actually arise out of that substance at the points d', d ! , fig. 3, 
Plate VIII. I have further ascertained that the decussating fibres from both the 
posterior and the anterior grey substances ascend toward the brain after they have joined 
the pyramids. There is another exceedingly interesting structure, which, although it 
does not share in the formation of the anterior pyramid, I shall mention here, because 
it is mixed up with the decussating fibres of those bodies in the lateral column. In fig. 
4, Plate VIII. on the right side, several curved bundles of fibres ( d ') may be seen pro- 
