CiiAo. vn. Structure of the Brain. 201 



Rcillestun, BIr. Marshall, M. Biora and Professor Turner. At tho 

 coinliisidu of a special paper on tliis subject the latter wriles:" 



•' The three specimeua of the brain of a chimpanzee just described, 

 •' prove, that the generalisation which Gratiolet has attempted to draw of 

 " the complete absence of the first oimnecting convolution and the 

 ■' concealment of the second, as essentially chariioteriscic features in the 

 " brain of this animiil. is by no meuns uni verbally iippliciible. In only one 

 •' specimen did Ihe brain, in these particulars, follnw the law which 

 " Gratiolet has expressed. As regards ihe pi esenee of the superior bridg- 

 " ini; convolution, 1 am inclined to think th;it it has existed in one ht mi- 

 ** sphere, al least, in a majority of the bruins of ihis animal which have, up 

 ■' to this time, bt en figured or described. The supei ficial position of the 

 " second bridging convolution is evidently less frequent, and has as yet, 

 " I believe, only been seen in the bra^n 'A) recorded in ihis communi- 

 " cation. The asymmetrical arrangement in the convolutions of the 

 •• two hemispheres, which previous observers hiive leferred to in ihtir 

 " descriptions is also well illustrated in these specimens.' (pp. 8, 9.) 



Even were the presence of the temporo-ocoipital, or external per- 

 pendicular, sulcus a mark of disanction between the higher apes an.l 

 man, the value of such a distinctive character would be lendered very 

 doubtful by the structure of the brain in the Platyrhine »pes. In fact 

 while the tempoixj-occipital is one of the most con.^tant of sulci in 

 the Calarhine, or Old World, a|ies, it is uevei' veiy sirongly developed 

 in the New World a|ies; it is absent in the smaller Plaiyihin, ; 

 rudimentary in Pithecia ;" and more or less obliterated by br.d^iiig 

 convolutions in Ateles. 



A character which is thus variable within the limits of a single group 

 can have no great taxonomio value. 



It is further established, that the degree of asymmetry of the convolu- 

 tion of the two sides in the human brain is subject to luueh individual 

 variation ; and that, in Ihose individuals of the Bushman race who have 

 been examined, the gyri and sulci of the two hemispheres are consider- 

 ably less complicated and more symmetrical tlian in the European 

 brain, while, in some individuals of the chimpanzee, their complexity 

 and asymmeti'y become notable. This is paiticularly the case in the 

 brain of a young male chimpanzee figured by M. Broca. (' L'ordre 

 des Primates,' p. 165, fig. 11.) 



Again, as respects the question of absolute size, it is established that 

 the difterence between the largest and the smallest healthy human 

 bruin is greater than the ditl'erence between the smallest healthy 

 human brain and the largest chimpanzee's or orang's brain. 



Moreover, there is one. circumstance in which the orang's and chim- 

 panzee's brains resemble man's, but in 'which they differ from the lower 

 apes, and that is the presence of two corpora oandicautia — the 

 tynomorpha having but one. 



In view of these facts I do not hesitate in this year 1874, to repeat 

 wid insist upon the proposition which I enunciated in 1863." 

 "•So far as cerebral structure goes, therefore, it is clear that man 



" Notes more especially on the " Flower. 'On the Anatomy 0/ 



oridgiag convolutions in the Brain Htheoia Monachus' ' Pi'oceedings oi 



cr' the Chimpanzee, 'Proceedings of the Zoological Society,' 1862. 



th( "oyal Society of Edinburgh,' " ' Man's Place in Nature,' p. 1C2 

 I860 



