THE BRAIN IN THE ANTHROPOMORPHA. 485 



jection of the iipwardly convex roofs of tlie orbits into 

 the cranial cavity. The posterior cornti of the lateral 

 ventricle is always well developed, and contains a pro- 

 minent hippocampus minor and eviinentia collateralis. An 

 occipito-temporal or "extei-nal perpendicular" snlcus is 

 always present. It is most nearly obliterated in the Orangs. 

 All the gyri of the human brain are represented in the 

 cerebral hemispheres of the Chimpanzee ; but they are 

 simpler and more symmetrical, and larger in proportion to 

 the brain (See Figs. 21 and 22). The fissure of Sylvius is less 

 inclined backwards, and that of Rolando is placed more 

 forwards than in Man. The insula has simpler and fewer 

 radiating sulci, and is not completely hidden by the temporal 

 lobe. Only the second, third, and fourth annectent gyri 

 appear upon the surface. The first remains folded upon 

 itself, and gives rise to the characteristically simian occiijito- 

 temporal or external perpendicular sulcus. The occipito- 

 parietal sulcus, on the inner face of the hemisphere, is 

 much more nearly perpendicular than in the human brain. 

 The corpus callosum is relatively smaller; the septum 

 lucidum is very thick, and the pre-commissural fibres are 

 well developed. The vermis is small in proportion to the 

 lateral lobes of the cei-ebellum, and the flocculi are rela- 

 tively small, and lie below the latter. 



The whole cerebellum is larger in proportion to the 

 cerebral hemispheres; the latter being to the former, as 

 8i to 1 in Man, bnt as 5| to 1 in the Chimpanzee.* The 

 nerves are larger in proportion to the brain than in Man. 

 There are no corpora trapezoidea, such as exist in the lower 

 Mammals, and the corpora albicantia are double. 



In all the Antliropomorpha, the inner incisors are lai'ger 

 than the outer, in the upper jaw ; smaller, in the lower jaw. 

 There is a diastema, though it is often but small in the 

 female Chimpanzees. The canines are large and strong, 

 and may be grooved longitudinally on their inner sides. 



* It must be recollected that the brains of young anthropomorphous 

 Apes, only, have been examined. Perhaps this has to do with the 

 absence of mineral deposits in the pineal gland of the Apes. 



