90 



ANATOMY OF VERTEBRATES. 



Perameles, Phalangers, and Koala, the hemispheres or lateral 

 lobes of the cerebellum are characterised by a small subspherical 

 lateral process or appendage, c, c, fig. 74, which is lodged in a 

 peculiar fossa of the petrosal above the internal meatus : there 

 are corresponding but less produced processes in the Dasyures and 

 Opossums, they do not project in the Wombat. On the upper 

 surface of the cerebellum the medullary substance or nucleus 

 appears superficially at a small tract on each side the vermiform 

 process, marked with an asterisk in figures 74 and 75. ! The 

 simple disposition of the arbor vitae is shown in fig. 46, e. 



In the Lissencephala, the cerebellum in the Insectivora, fig. 76, 

 and Cheiroptera, resembles that of the Opossums; in the Rodentia 

 the lateral lobes, fig. 59, d, show a greater increase, which is most 

 marked in the swift running Hares, fig. 81 , /, /. As this develope- 

 ment is not accompanied with a concomitant growth of the cere- 

 brum, the cerebellum is proportionally greater to the rest of the 

 brain in Rodents than in other mammalian orders. 



The Cetacean brain is remarkable for the large propor- 

 tional size of the cerebellum, fig. 60, and especially of its lateral 

 lobes, c. On the under surface may be distinguished the main 

 part of the lateral lobe, e, the oblique lobule, f, that which answers 



to the * amygdaloid lobe ' and the 

 ' floccus ' of Reil, h. Each is sub- 

 divided by the chiefly transverse 

 anfractuosities into numerous la- 

 mellae. The middle lobe, fig. 93, a, 

 is not symmetrical but inclined, 

 like the skull, to one side, in Del- 

 phinus. The grey nucleus or ( cor- 

 pus fimbriatum ' is well developed. 

 The ' pons,' fig. 60, c, is now large 

 and prominent. 



In the Ungulata, the relative size 

 of the lateral lobes increases with 

 the bulk of the species, and attains 

 its maximum in the Elephant ; in 

 the Rhinoceros, Giraffe, fig. 86, Ox, 

 and Horse, fig. 61, the middle lobe 

 is contorted, especially above. The 

 common castration of the latter 

 quadruped has afforded abundant evidence that the cerebellum is 

 in no degree affected thereby in size or form. 2 



1 lxx-. pi. v, figs. 3 and 4. » xli". 



Upper surface of the brain, Agouti. 



