518 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
cutaneous coverings, act as buffers to the delicate temporal walls, which, in some 
places, do not exceed a line in thickness. Thus, while the brain is provided against 
lateral concussions, the very utmost limit is given it as regards breadth, and this 
without diminishing the space necessary for the muscular apparatus, or increasing the 
width of the hinder portion of the head, which altogether is comparatively narrow 
and elongate. 
On the dura mater being longitudinally divided and laterally reflected, a sketch was 
made of the brain in situ. In this way the upper convolutions, sulci, and general rela- 
tion of parts previously to change of position were secured. After this the brain and a 
small portion of the upper part of the cord were carefully removed in the usual way, 
then weighed with the membranes, and preserved in spirit. 
The dura mater of the base being left within the cranium, and the calvarium replaced, 
an accurate model of the interior was obtained by filling the cavity with plastic mate- 
rial. From this a mould was formed, and, lastly, a plaster of Paris cast derived there- 
from. As is well known, the recent brain immediately on removal alters in shape ; and 
still more so, as Marshall’ has accurately noted, does the preserved encephalon change 
remarkably in the relations of its parts. A photograph could not conveniently be taken 
at the moment. ‘The figures here given, therefore (figs. 38, 39, & 40), of the lateral, 
upper, and basal views, are rigorously measured outlines, by my friend and artist Mr. 
Berjeau and myself, of the intercranial cast, filled in their details from the shrunken 
brain, corrected by the sketches made of the organ in its fresh condition. If not perfect 
counterparts, the figures will be found close approximations to the natural aspect of each 
view in question. The longitudinal and horizontal sections (Pl. LXXIX. figs. 44, 45) 
are from the preserved hardened brain, very slightly modified by reference to a similarly 
divided soft intracranial model. 
It is but proper for me to express my sense of obligations to recent workers on cerebral 
anatomy, among whom more particularly may be mentioned Leuret’, Gratiolet*, Dareste*, 
Owen®, Huxley®, Flower’, Marshall’, Turner®, and Rolleston”. 
2. The Dura and Pia Mater. 
The most external fibrous cerebral envelope, the dura mater, is firm and of moderate 
thickness. Its upper surface is very irregularly indented, corresponding as it does to 
the greatly convoluted brain, and more particularly to the unequally hollowed and 
ridged bony vault. Minute vascular channels exist plentifully over the greater part of 
1 Nat. Hist. Review, 1861, p. 298. ? Anat. Comp. d. Syst. Nerv. Paris, 1839-57. 
* Mém. sur les Plis céréb. de ! Homme &c. * Ann. Se. Nat. 4th ser. iii. 1855, p. 73. 
’ Trans, Zool. Soc. vol. i. 1833, ‘‘ Cheetah ;” and his ‘ Anat. of Verteb.’ vol. iii. &c. 
§ Brain of Ateles, P. Z. 8. 1861, p. 259: his Hunterian Lectures, &c. 
7 Phil. Trans, 1852, p. 185. Trans. & Proc. Zool. Soc., various papers. § Phil. Trans. 1865, p. 501. 
» Proc. Roy. Soc. Edinb, 1865-66, vol. vy. p. 578, &e. 10 Nat. Hist. Review, 1861, p. 201. 
