156 TH"E HUMAN SPECIES 



evolved through graduated modifications from the same type 

 as that from which the rest of the Primates have sprung. 



As early as 1866, in his Lemons sur la Physiologic (p. 890), 

 Vulpien remarks : " Les differences reelles, qui existent entre 

 1'encephale de 1'homme et celui des singes superieures, sont bien 

 minimes. L'homme est bien plus pres des singes anthro- 

 pomorphes par ses caracteres anatomiques de son cerveau, que 

 ceux-ci ne le sont seulement des autres mammiferes, mais 

 meme de certains quadrumanes, des guenons et des macaques." * 

 In Huxley's opinion, the anatomical differences between the 

 brain of the highest apes and that of man consist, broadly 

 speaking, of the superior size, absolute and relative, of the 

 hemispheres of the human cerebrum, as compared with those 

 of the orang and chimpanzee, in the smaller cavity of the 

 human frontal lobes, caused by the upward projection of the 

 supraorbital ridge, in the abundance of the human convolutions 

 and fissures of the secondary folds together with less symmetry 

 in their order and in the usually slight development of the 

 human tempero-occipital fissure. As further distinction 

 Wiedersheim - adduces the fact that the third frontal fold in 

 the anthropoid brain differs from that of man in that a small, 

 isolated gyrus occurs at the base between the sulcus fronto- 

 orbitalis and the sulcus opercularis. This gyrus forms the 

 surface of the insula cerebri. In all apes the insula lies deep 

 and shows an inferior development to that of man. The 

 anterior region of the insula, like the operculum, has been 

 acquired during the later periods of man's history undoubtedly 

 in connection with the development of the organs of speech 

 (see Fig. 81). 



The finer anatomical distinctions in man's favour are based 

 on differences in the structure of the cortex cerebri, the most 

 important psychical organ. With respect to the structure of 

 the brain, the mammals are divided into two great classes, the 

 Gyrencephala and Lissencephala. In the Gyrencephala (apes, 



1 " The actual differences existing between the brain of man and that of the 

 higher apes are extremely slight. Man is much nearer the anthropomorphous 

 apes, as regards the anatomy of his brain, than are the latter not only to the 

 other mammals but even to certain of the quadrumana, the long-tailed monkeys 

 and the Macacus species." 



2 Wiedersheim, loc. cit., p. 137. 



