Scottish National Antarctic Expedition : Observations on the Anatomy of the 

 Weddell Seal (Leptonychotes Weddelli). Part IV. : The Brain. By David 

 Hepburn, M.D., C.M., Professor of Anatomy, University College, Cardiff (University 

 of Wales). (With One Plate.) 



(MS. received June 18, 1912. Read December 2, 1912. Issued separately February 8, 1913.) 



The material placed at my disposal for the purposes of this paper comprised the brains 

 of four adult specimens of the Weddell seal, in addition to the brain of the young 

 animal which has formed the subject of my former contributions.* The four adult 

 brains having been removed at the time the animals were killed, and preserved in a 

 solution composed of spirit (90 per cent.) 6 pints and formal (2 per cent.) 4 pints, 

 were, with one exception, in a firm and satisfactory condition for detailed anatomical 

 examination. The body of the young seal had been preserved with a view to ordinary 

 dissection, and therefore its brain was not in the firm state of the adult specimens ; but 

 as I had the opportunity of removing this brain from the skull, 1 was able to observe 

 the disposition of the dura mater to the hemispheres of the cerebrum and cerebellum. 

 While the dura mater presented, as a whole, its usual arrangements, it was noteworthy 

 that the falx cerebri did not act as a septum between the two hemispheres of the 

 cerebrum except to a very slight extent, and certainly for not more than one-third of 

 the distance between the vertex of the cerebrum and the dorsal surface of the corpus 

 callosum. As a result, in the region referred to the opposing mesial surfaces of the 

 two hemispheres lay not only in close apposition with each other, but their convolutions 

 were intimately adapted to each other. Similarly, the tentorium cerebelli only extended 

 a short distance between the cerebrum and the cerebellum, and, as the occipital ends of 

 the cerebral hemispheres fell considerably apart from each other, there was space for 

 the accommodation of the well-developed vermis of the cerebellum as well as for the 

 bulbous pineal body, which occupied a position upon its dorsal aspect. As I removed 

 the brain from the skull the stalk of the pineal body gave way, and probably the same 

 thing had occurred during the removal of the adult brains, for, while different lengths 

 of the stalks had been preserved, there was only one complete specimen of its bulbous 

 extremity. Looked at from the vertex, the general outline of the whole brain was that 

 of a four-sided figure with rounded angles, and the cerebral hemispheres concealed the 

 cerebellum except where the vermis was exposed between them at their occipital ends. 

 The frontal ends of the hemispheres were not rounded into frontal poles ; but, on the 

 contrary, they almost formed Hat frontal surfaces. Similarly, the occipital ends were 

 rounded and not pointed to form occipital poles. There was a small amount of differ- 

 ence in the absolute size of the adult brains, and the largest specimen measured 120 mm. 



* Part I., Tram. Roy. Soc. Edin., vol. xlvii. p. 57, 1900. Part II., Tniim. Hoy. Soc. Edin., vol. xlviii. p. 191, 1912. 

 Part III., Trns. Unit. .SW. AVi'., vol. xlviii. p. 321, 1912. 



(REl'RINTED FKOil TUE TRANSACTIONS OF THE HOVAL SOCIETY OF EDINBURGH, VOL. XLVIII., PP. 827-847.) 



