Nervous System Special. 127 



in the still greater proportional size of the cerebrum to the rrst 

 of the brain, viz. as 8 to 1. The anterior commissure has but 

 insio^nificant dimensions. The cerebral hemispheres completely 

 overlap the cerebellum : the middle lobe is well defined. 



ii. Qiiadrumana. Membranes. In the matter of the * crisl a 

 galli,' see Bimana. In Cebus and Ateles the tentorial margin of 

 the petrosal is slightly produced. Epencephahn. In the Anthro- 

 poid Apes the arciform disposition of fibres in conjunction with the 

 olivary bodies prevails instead of the ' trapezoid ' found in all other 

 Orders below. The 'appendicular lobe' of the cerebellum is present 

 in most Lemurida) [e.g. Aye Aye), and is lodged in a special pit of 

 the petrosal : but in the large Catarrhiua the lateral lobes increase 

 in size, and lose or incorporate the appendix. The flocculus is pre- 

 sent in all Quadrumana, and is well ma ked in he timid and sharp- 

 eared nocturnal Aye Aye. Prosencephalon. In the Lemurida) the 

 cerebrum does not extend over the whole of the cerebellum. In 

 the diminutive Midas the upper surface of the hemispheres is 

 smooth. The brain of several genera of Apes reeembles that of Man* 

 in the posterior development of the cerebral hemispheres specialized 

 as the * third lobe ; * in the possession of a posterior horn to the lateral 

 ventricle {e.g. in Orang-utan) ; and in the presence of a hippocampus 

 minor (Orang-utan)f . 



iii. Insectivora. All the four primary segments are in view from 

 above and succeed each other from behind forward (e.^. Ehynchocyon, ' 

 African shrew) as in Reptilia. Epencephalon. The cerebellum 

 presents few transverse convolutions ; the median, or vermiform lobe 

 is large relatively to the lateral lobes ; he pons rather small. Mesen- 

 cephalon. The corpora quadrigemina;]: are large and exposed between 

 the cerebrum and cerebellum. Prosencephalon. The cerebrum does 

 not extend over the cerebellum ; each hemisphere is much contracted 

 anteriorly. The corpus callosum is of limited extent; the hippo- 

 campi relatively large : there is no septum lucidum. The lateral 

 ventricles are continued into the rhinencephalon. The cerebral 



* Huxley. Comp. Anat. (Ed. 1864) pp. 98-100. 



t For the complete elaboration of the comparison of the convolutions of the 

 Brain of Man as compared with that of the Apes the student should consult M. 

 Pierre Gratiolet's " Memoire sur les Plis Cerebraux des Hommes et des Primates," 

 of which the Appendix to this chapter is a summary. 



X The 'optic lobes' of Talpa show no reduction of bulk commensurate with 

 that of the visual organ. 



