BRAIN OF MAN AND THE BRAINS OF CERTAIN ANIMALS. 41 



To commence with the lobe which is lettered a and /3 in our dia- 

 grams, which occupies so much space and has had so much importance 

 assigned to it in the human brain, alike by Professor Huxley ('Natural 

 History Review/ January 1 86 1 ) and M. Gratiolet ('Memoire,' p. 62), 

 what is its meaning, signification, Bedeutung? is its importance serial 

 or physiological, classificatory and specific, or functional and quanti- 

 tative ? M. Gratiolet's works give, it must be said, but one uncer- 

 tain sound upon this point. Twice ('Memoire,' pp. 89 and 76) he 

 tells us that the Thumbless Spider Monkey (Ateles helzebutli) possesses 

 'par un exemple unique parmi les singes,' these convolutions in as 

 perfect a state of morphological integrity as man himself, albeit one 

 of them may be 'fort reduit? On the other hand, I find M. Gratiolet 

 (in the 'Memoires de la Societe de l'Anthropologie/ i860, torn. i. 

 p. 65) speaking of the coming level to the surface of one, the second 

 of these bridges, as a character peculiar to man. And as if to put 

 himself again in opposition to himself, I see in one of his own figures 

 of a human brain, and that a well-developed one (Plate II. Fig. 1), 

 a long unbridged fissure running continuously from this internal 

 perpendicular fissure right across the upper surface of the hemi- 

 sphere. In this last case, however, I suspect that, as is described 

 by myself in the 'Natural History Review, 5 April, 1861, p. 211, the 

 brain in question having belonged to a gardener, and a man of 

 more than ordinary intelligence, this appearance of an unfilled-up 

 chasm is due to excess rather than to defect of development ; the 

 bridging convolution, instead of crossing from one side directly 

 to the other, having bent itself into a curve with its concavity 

 upward so as to form thus a secondarv valley within the primary 

 fissure, an appearance almost unavoidably deceptive in a hardened 

 and undissected brain. Professor Huxley, whose views as to the 

 importance of this lateral perpendicular fissure I just now alluded to, 

 seems in a recent number of the Zoological Society's 'Proceedings,' 

 June 1 1 , 186 1, to consider this part of M. Gratiolet's analysis as some- 

 what unsatisfactory, and his identifications of these bridging convo- 

 lutions to fall somewhat short of the certainty which attaches 

 usually to his homologies. Still in his figures of the Coaita [Ateles 

 paniscus) the occipital lobe is continuous with the parietal by a level 

 table-land summit. Coupling the authority of others with observa- 

 tions of my own, I shall be inclined to rank the physiological value 

 of these convolutions a and )3 as second only to those of the frontal 



