NERVOUS SYSTEM AND GENERAL SENSATION. 



49 



symmetrical ; the cerebellum is relatively larger to the cerebrum 

 than in man ; the trapezium, which is present in the lower 

 monkeys, is absent in them, as it is in man ; corpora albicantia 

 are distinct; the posterior cornu of the lateral ventricle becomes 

 developed with the pes hippocampi of the cornua ammonis, 

 parts which are only found in the human brain besides. 



Fig. 32. 



Fig. 33. 



TV' 



Brain of Cercopithecus Sabeeus 

 laid open. 



a 



Base of the same brain, showing 

 the cerebral nerves. 



[ 97. CEREBEAL NERVES. We have shown in fig. 20 the 

 primary course of the cerebral nerves, and their union with 

 the brain. The olfactory ganglia are large in the cold-blooded 

 vertebrata, but very small in man, consisting merely of an en- 

 largement of the trunk of the olfactory nerves (1), which are 

 the first pair that unite with the brain. From the olfactory 

 ganglia, reposing on the cribriform plate of the ethmoid bone, 

 numerous fine filaments proceed to the nasal cavity, and are 

 distributed to the mucous membrane of the nose. 



[ 98. The optic nerves (2) may be traced from the globe 

 of the eye to their union with the optic lobes, which are de- 

 veloped in a direct ratio with these nerves ( 88). Behind 

 the eye we observe the third, fourth, and sixth pairs of 

 nerves. 



[ 99. The third pair are the principal motory nerves of 

 the muscles of the eye : they distribute branches to the three 

 recti, and the inferior oblique muscles, and send fibrils to regu- 

 late the motions of the iris. Reflex motions of the parts to 







