DR. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 527 



What for convenience of description I have termed lobules of the antero-, post- 

 parietal, angular, and postteniporal gyri on the right face thus notably differ. Moreover 

 it becomes a moot point whether in the area in question parts of these so-called lobules 

 are not of a verity representatives of " plis de passage " of the French, " connecting" or 

 " annectant " gyri of English authors, as found in man and m-onkeys. In MM. Leuret 

 and Gratiolet's grouping of mammals according to brain-convolutions, they give the Seal 

 a high place, and separate it from the Carnivora by the Edentata, Marsupialia, and 

 Ruminantia. But some of the Ursidse lead towards the Pinnijiedia in their gyral 

 condition ; so that the series from the smoother, simpler-brained Felidee is really less 

 interrupted than their arrangement would warrant'. 



g. Interior structures. — On removing a horizontal section, about half an inch iu 

 thickness at deepest, from the upper face of the left hemisphere, the so-called centrum 

 ovale minus of Vicq d'Azyr was exposed. The white matter of the brain here presented 

 an elongated and transversely narrowed surface, deeply indented externally by the sulci 

 and convolutions, and somewhat less so internally by the fold bordering the interhemi- 

 spherical fissure. In the preserved brain in which the section above described was 

 made, the central substance was not pure white, but of a pale yellow hue, while the 

 cortical grey matter had a fawn tinge, shading in some places insensibly into the 

 yellowish centre. The darkness of the white matter, though in part due to the brain 

 having been soaked in spirit, was not entirely so produced ; for in the fresh condition I 

 observed that the variation between the central and cortical substance was less marked 

 than in a human subject of the Caucasian variety. The layer of grey matter had a 

 relative depth of -3% of an inch ; and, excepting a limited area, there was little appre- 

 ciable deviation between the different regions. 



A second, deeper horizontal slice laid open the lateral ventricle. This ca^'ity, com- 

 pared with the size of the brain, is large, and has a very marked /-shape. Its total 

 length in a straight line is 2-2 inches; but measured curvilinearly, the body of the 

 lateral ventricle is 1-1 inch long, the anterior cornu 0-6, and the posterior cornu 0-9 inch. 

 As regards the relative position of the extremities of the lateral ventricle to those of the 

 hemisphere, the posterior cornu approaches within 0-7 inch of the occipital lobe, the 

 anterior comu 0-8 inch from the anterior end of the frontal lobe. Thus the ventricle 

 is situated nearly equidistant between the front and back of the cerebrum. 



The anterior cornu has an obtusely rounded boundary in front, and is a fossa of 

 moderate depth. The corpus striatum is smooth- surfaced and slightly convex; it 

 measures in the opened ventricle 0-65 inch antero-posteriorly, and 0-4 inch transversely. 

 Proceeding from the foramen of Monro, the choroid plexus, as usual, traverses the 

 lateral ventricle in an oblique direction, externally and behind dipping into the descend- 



' The most admirable investigation of Prof. Gervais, " Mem. sur les Formes Cereb. propres aus Camir. Viv. 

 et Foss.," Nouv. Archiv. tom. vi. 1870, is weU worthy of reference. Coming late to hand, I could not avail 

 myself of its contents as I could have desired. 



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