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Show 314 ON THE BRAIN OF THE AFRICAN ELEPHANT. [Mar. 28, above; when viewed from behind the median lobe is concealed by the lateral lobes, which completely cover it over. Each of the lateral lobes is divided by a number of deep cross-running furrows. These are placed at irregular intervals, though parallel in direction; the cerebellum is thus divided up into a series of flat plates of varying thicknesses. Some of these fissures, which are all very deep, are not continuous right round the cerebellum ; the majority of them, however, are. The two halves of the cerebellum are not symmetrical as regards the furrows. The plate-like discs, in which the lateral lobes are cleft, are about 18-20 in number. The small median lobe of the cerebellum is in marked contrast to what is to be met with in, at any rate, many Ungulates and Carnivora. Remarks upon the principal Sulci. The preceding is, I believe, so far as it goes, an accurate description of the principal furrows. It now remains for me to attempt to determine which are the most important of these. Krueg indicates five furrows of first-rate importance in the brains of both African and Indian Elephants :- (1) Sylvian fissure, divided below into processus anterior and processus posterior, which join above to form processus acuminis. (2) Pre-Sylvian fissure. (3) Posterior supra-Sylvian fissure. (4) Sutural fissure. (5) Coronal fissure. The diagrams do not seem to m e to bring out close resemblances between the Elephantidae and the other mammals (Carnivora, Hyrax) with which they are compared. Dr. Krueg, however, considers that there are no characters peculiar to the Proboscidian brain, but that they approach the Carnivora more nearly than they do the Ungulata. In the brains of the Carnivora tbe furrows on the surface of the brain have an arcuate arrangement round the Sylvian fissure. In the Ungulata, as in the Rodents, the longitudinal fissures seem to be straighter and not to present, at any rate in so marked a degree, an arch-like course. I admit, however, that the great development of the temporal lobe in the Elephant is a point of resemblance to the Carnivora (also of course to the Primates, which rather takes away from its significance), and that the furrows of tbe African Elephant's brain, as I read them, are more decidedly arcuate than they are represented to be by Krueg. But it is so extremely difficult to compare tbe furrows of a complexly convolute brain with those of a smoother brain that I refrain from venturing upon a definite opinion as to the affinities indicated by the study of the Elephant's brain. I can identify all the fissures drawn by Krueg, with the exception of the anterior (or posterior, as the case may be) branch of the Sylvian. I could not see quite so marked a superficial boundary |
