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2 JoURNAL OF COMPARATIVE NEUROLOGY. 
the optic chiasma. The crura of Macacus are not visible on 
the base of the brain. They are entirely hidden from view by 
the well-developed temporo-sphenoidal and the occipital lobes. 
In contradistinction to dog and man Macacus presents but a 
single corpus albicans, which occupies a mesial position. We 
naturally expect to find a well-developed olfactory apparatus in 
dogs; and such is the case, for the olfactory bulb projects be- 
yond the hemispheres. The olfactory lobes, the bulbs and the 
olfactory tracts of Macacus are greatly atrophied. Compared 
with the dog the orbital surface of the frontal lobe has likewise 
retrograded. 
The Hemispheres. 
The growth backward of the body of the lateral ventricle 
in Macacus results in the formation of a posterior cornu, and 
gives us an additional lobe, the occipital. The occipital lobe is 
merely a differentiation of the posterior part of the parietal lobe. 
In Macacus it is very extensive, comprising about a third of 
the entire hemisphere. In man the occipital lobe comprises 
less than a sixth of the secondary fore-brain. 
The hemispheres of Macacus are in contact with one 
another throughout their entire extent; even the apical portion 
of the frontal lobes are contiguous. In the dog the frontal 
apices are slightly separated, and the rounded posterior extrem- 
ities of the parietal lobes diverge considerably to permit of the 
reception of the worm of the cerebellum between them. The 
entire hemisphere of Macacus is slightly curved from before 
backwards. This is most marked in the frontal lobe, where 
the apex curves sharply downwards in a hook-like manner. 
This curve is due to the non-development of the orbital sur- 
face. Externally the frontal lobes are flattened. The parietal 
and the occipital lobes are curved only slightly. 
The arrangement of the fissures and the convolutions of 
Macacus closely resembles the condition met with in the human 
foetus. The numerous annectent gyri of the adult human 
brain renders it difficult to homologize the gyri of the adult 
brain with those of Macacus. The Sylvian, the Rolandic, the 
