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 1 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 (PI. 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 2 , Gratiolet 3 , Dareste 4 , 

 Owen 5 , Huxley' 5 , Flower 7 , Marshall', Turner 9 , and Kolleston 10 . 



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. a Anat. Comp. d. Syst. Nerv. Paris, 1S3U-57. 



3 Mem. sur les Plis cereb. de l'Honinie &e. i Ann. So. Nat. 4th ser. iii. 1855, p. 73. 



s Trans. Zool. Soc. vol. i. 1833, " Cheetah ; " and his ' Anat. of Verteb.' vol. iii. &e. 



' Brain of Ateles, P. Z. S. 1861, p. 25U : his Hunterian Lectures, &c. 



7 Phil. Trans. 1852, p. 185. Trans. <fe Proc. Zool. Soc, various papers. 8 Phil. Trans. 1865, p. 501. 



5 Proc. Roy. Soc. Edinb. 1865-66, vol. v. p. 578, &c. 10 Nat. Hist. Review, 1861, p. 201. 



