BRAIN OF MAN AND THE BRAINS OF CERTAIN ANIMALS. 37 



when we analyse the tertiary convolutions. In one part of the 

 brain, where two of the five great masses into which its convoluted 

 surface may be mapped out abut upon each other, what are but 

 connecting' spurs in the ape's, overhung and concealed by the 

 beetling parietal and occipital lobes, rise in man to the dignity of 

 connecting table-lands, rilling up and bridging over levelly what is 

 a valley, or rather a chasm, in most simious encephala. Small as 

 this difference may seem to be 1 , it nevertheless corresponds with 

 what has been spoken of as absolutely, with two other points, 

 differentiating man's brain from that of the ape's under the head 

 of 'the absence of the external perpendicular fissure/ and it cor- 

 responds also with the absence or presence of what has been figured 

 in diagrams 3 and 5 in a larger or smaller mass of convolutions 

 lettered a and /3. These diagrams I must now proceed to explain 

 by the aid of the yet simpler, yet not less truthful Figures 6 and 7. 

 These last figures are taken from M. Gratiolet's work so often 

 referred to, but they might have been taken from the outer aspect 

 of the left cerebral hemisphere of the very brain from which the 

 dissected right ventricle of Figure 6 was drawn. The oblique line 

 which is lettered S, in what I will speak of as a vervet monkey's 

 brain, is the fissure of Sylvius. Earliest to appear in the developing 

 brain, it is the very last convolution which we lose in the simplified 

 cerebrum of the lowest western monkey. From both the stand- 

 points, therefore, of scientific anatomy, it is of primary importance, 

 and to us it is the least moveable of all our land-marks. As it 

 rises and forms an angle with the horizon, so the grade of the 

 brain to which it belongs falls, and vice versa. Our second land- 

 mark is the fissure which is second also in order of appearance in 

 the growing human, though not in the simious brain, the fissure of 

 Rolando. It is a fissure which should be dear to the phrenologist, 

 for whilst all other fissures and their limiting convolutions shift 

 (Gratiolet's ' Systeme Nerveux,' tome ii. p. 115) about in different 

 individuals as they are differently developed, from one region of 

 the protecting skull roof to another, so that we are never justified 

 in saying that any one convolution, which we could recognise and 

 number accordingly in an exposed brain, will be found under such 

 or such an osseous protuberance, which we may be passing our 

 finger over (' promenant nos aveugles doigts,' as Gratiolet some- 



1 'Nat. Hist. Keview,' January, 1 861, p. 83. 



