804 THE BRAIN OF QUADRUMANA. 



the Gorilla, and the Orang, are not in all cases the same, 

 the reader will have little difficulty in recognizing in each 

 the parts which correspond. 



No great difference exists between these three Apes in 

 regard to the Internal Topography of their brains, so far 

 as it is known. The following particulars refer in the 

 main to that of the Chimpanzee (fig. 115). 



The Corpus Callosum is shorter and thinner than in 

 Man, and Prof. Marshall concludes that, in proportion to 

 the size of the brain, its bulk is twice as great in Man as 

 it is in the Chimpanzee. The Anterior Commissure is 

 proportionally large, and so is the soft or Middle Com- 

 missure. The Posterior Commissure, however, is small. 

 The Fornix is thin, and the ' tenia semicircularis ' is 

 just discernible as a thin white band lying over the 

 line of junction between the Thalamus and the Corpus 

 Striatum, and joining the pillars of the Fornix an- 

 teriorly. 



The Lateral Ventricles are rather large, and its three 

 Cornua are quite distinct. The central part, known as 

 the body of the ventricle, corresponds with the parietal 

 lobe externally; its anterior cornu is prolonged into 

 the frontal lobe ; its descending cornu traverses the tem- 

 poral lobe, and its posterior cornu extends into the occi- 

 pital lobe. On the inner side of the descending cornu is 

 the projection (fig. 115, c a), known as the ' Hippocampus 

 major,' from which the posterior pillar of the fornix is 

 derived. On the inner side of the floor of the posterior 

 cornu is the ' Hippocampus minor' or 'calcar avis,' a small 

 eminence (h m), produced by a deepening of part of the 

 fissure of the hippocampus (the ' calcarine '), to which it 

 corresponds externally. Between this projection and the 

 upper part of the bend of the larger Hippocampus is 



