36 ON THE AFFINITIES AND DIFFERENCES BETWEEN THE 



existing between the vertical radii of the orang and man severally. 

 The frontal lobe was, however, in this respect, more markedly 

 inferior in the African ape considerably than was his parietal ; but 

 for the explanation of these terms I must enter upon my third 

 head, that, namely, of the differences which M. Gratiolet's analysis 

 of the convolutions has enabled us to discover and describe. As it 

 will henceforth be an impertinence in any one to write or speak 

 upon the science of language without a due acknowledgment of his 

 obligations to the lectures delivered upon that subject in this place 

 by Professor Max Miiller, so it would be an affront to the under- 

 standing and information of any scientific audience to address them 

 upon the subject of the brain and ignore M. Gratiolet's labours. 

 His ' Memoire sur les Plis Cerebraux de l'Homme et des Primates/ 

 published some eight years ago, is but a short treatise. Short 

 treatises have, however, before now, revolutionised sciences. 



The convolutions into which the exterior of the brain is folded 

 are of three orders, primary, secondary, and tertiary. They are 

 divided from each other by correspondingly winding indentations. 

 The primary convolutions may be compared to the great ridges 

 which in a mountainous country, running more or less parallel to 

 each other and forming blocks and masses of more or less divergent 

 directions, give it its distinctive geographical character. The 

 secondary convolutions may not inadequately be represented by the 

 indentations which we find on the broader table-land summits of 

 many, if not all, of such ranges. Finally, the spurs which run 

 down and interlock with similar spurs from opposite ranges may 

 be taken as representatives of the tertiary convolutions. That 

 such details, as I shall have time to go into, may become possessed 

 of meaning and interest sooner than without such a statement they 

 would be, I will say, that the primary convolutions, the great 

 typical lines and ridges, are the same in the brains of the apes and 

 in our own. 'L'homme,' say the Dutch anatomists already referred 

 to ('Nat. Hist. Rev.,' No. V. p. 117), ' n'a rien dans son ence*phale 

 qui manque absolument aux singes/ The table-land summits may 

 have their long backs but shallowly or not at all indented in the 

 one class, while in the other they may be cleft down into as sheer 

 and deep fissures as are the primary valleys themselves, but the 

 general arrangement is the same in both in spite of these merely 

 quantitative differences. The case, however, is somewhat different 



