268 ME. J. L. CLAEKE ON THE INTIMATE STETJCTUEE OE THE ERA TN. 
in the inner side of the restiform body, and exposed by the removal of 'the posterior 
pyramid. From the upper end of this fusiform grey mass a thin but broad layer of 
fibres, mixed with some grey substance (p), radiates upward and outward on the resti- 
form body (see also p, fig. 24). 
Fig. 14, Plate IX. is another careful dissection of some of these parts. The pos- 
terior pyramid (b) has been separated on the left side of the medulla from the inner side 
of the posterior column (<?), and drawn aside, exposing nearly the whole of the continuous 
tract of grey substance constituting below, the spinal-accessory nucleus (t), and above, the 
vagal nucleus (g). This grey tract is intimately connected and continuous at the point 
of the calamus with the posterior pyramid (5), which sends forward into it a series of 
fine fibres. It is composed of round, oval, crescentic, or angular cells of large size, and 
a multitude of very fine fibres, of which a large number are longitudinal, and ascend 
with an inclination outward from t to the calamus scriptorius at _y, where those on the 
outer side are connected with the posterior pyramid, from which again a bluish process 
runs forward to the oval or vagal mass left uncovered by the posterior pyramid at g, as 
shown in fig. 12. 
(11) I will now briefly describe, in a series of transverse sections, the medulla oblon- 
gata of the Monkey, not only because’ it exhibits certain interesting deviations from the 
appearances observed in Man, but because it illustrates in a beautiful manner the highly 
important morphological changes which I have just been endeavouring to explain. 
In the lower kind of Apes it differs considerably in shape from the human medulla, 
the antero-posterior diameter being less than the lateral, but proportionably greater 
than in other animals. The form and arrangement of its different parts may be consi- 
dered to possess a kind of intermediate character between man and the higher mammalia. 
The anterior pyramids and olivary bodies are proportionably larger than in any inferior 
animal, and, as in Man, are the chief cause of the increase in the antero-posterior dia- 
meter of the medulla. The posterior and lateral white columns are largely developed 
and very distinctly marked off from each other by indentations, as in some of the mam- 
malia, especially of the feline species. Fig. 15, Plate IX. represents the grey substance 
at the lower part of the medulla on a level with the points of the anterior pyramids. 
It has a greater resemblance to the corresponding portion in Man than in any other 
animal, but it differs from both in being pierced behind the canal by a greater number 
of longitudinal bundles of fibres, represented by the four dark dots * ; d" is a close net- 
work with nerve-cells springing out of the side of the anterior cornu, and forming, 
higher up, the lateral nucleus. Fig. 16, Plate IX. is an exact representation of the grey 
substance at a level corresponding very nearly to the same part in fig. 4, Plate VIII. of 
the human medulla. Fig. 17, Plate IX. shows both the white and grey substances still 
higher up, at a point nearly corresponding to that of fig. 5, Plate VIII. Here it will 
be seen that the posterior pyramids {b, b), and especially the restiform bodies (c, c), are 
largely developed. The lateral columns (d, d) are particularly large, and the posterior 
* The same letters indicate the same parts as in all the preceding figures of the human medulla. 
