OF THE ORANG TJTANG. 9' 



belief that the cerebral hemispheres of the apes bulge less laterally 

 than do those of man ; that they are not merely more boat-shaped, 

 and tapering anteriorly and posteriorly, but that they are more 

 wall-sided, and less protuberant laterally. 



Though we may be inclined to consider the diminution in lateral 

 expanse, and in backward growth of the posterior lobes, D, of which 

 our figures speak, as an individual rather than as a specific pecu- 

 liarity, we are impelled to assign greater importance to the cur- 

 tailment in downward growth to which they, as well as other 

 similar figures, testify. A line drawn along the edge of the cerebral 

 hemisphere in Fig. i, where that hemisphere overlies the cerebellum, 

 will be seen to be much less clearly horizontal than a line is, which 

 holds the same relation in a human brain. It seems as if the 

 cerebellum had encroached upon the cerebral lobes which roofed it 

 over. 



The same figure shows that a similar stunting has befallen the 

 upward growth of both the frontal and posterior lobes, a line 

 bounding the superior edge of the hemispheres from D forwards to 

 A, describing a much more even curve than is usual in man. 



Less ambiguously does the vertical direction of the fissure of 

 Sylvius F, and of the convolution, 6, 6, 6', parallel with and im- 

 mediately below the lower lip, 7, 7, 7, of that fissure, speak of 

 diminished relative antero-posterior growth of the frontal lobes. 

 The greater relative thickness of the nerves is well seen in Fig. 2. 



These nine points of greater or less discrepancy between the 

 human and the simious brain may be arranged under our first head ; 

 they consist, in the ape, of diminution in downward, lateral, up- 

 ward and antero-posterior growth, first, of the posterior, secondly, 

 of the frontal lobes ; and to these, based on consideration of dimi- 

 nution, we have to add the ninth, based upon a consideration of 

 increase, that, viz. of the size of the nerves. What is the value of 

 these points as differentiating characteristics? Two canons may 

 be laid down to assist us in estimating the value of such character- 

 istics as means for settling the relative rank of rival organisms. 

 The first of these may be thus expressed : — If certain struc- 

 tures, or certain relations of certain structures, are found to exist 

 in animals confessedly lower in the scale of life than those which 

 are the subjects of comparison, the presence of such structures, 

 or of such relations of structures, cannot by itself be held to be a 



