258 DIVERSIONS OF A NATURALIST 



on one common plan in the group of monkeys and man 

 a plan differing from that seen in other groups which 

 have a convoluted brain-surface for instance from that 

 seen in the carnivora (dogs, bears, and cats) and again 

 from that seen in the ungulates (hoofed mammals). 

 The convolutions of the brain of the higher apes 

 have been minutely compared with those of man's 

 brain. The two sets of convolutions agree very closely, 

 but are less extensive in the apes and certain small 

 tracts of convolutions present in man, are deficient in 

 the apes, especially in the frontal region and at the 

 hinder or occipital region. We know very little of the 

 exact significance of each region of convolution in the 

 brain. The existence of convolutions separated by 

 furrows ^ clearly enough increases the amount of surface 

 of the brain, which consists of a grey substance called 

 " the cortex of the brain," and is known to be a peculiar 

 and specially active material. The mere comparison of 

 the size and height of the frontal region in different 

 animals and in man justifies the conclusion that an 

 increase of this part of the brain is more especially re- 

 lated to increased intelligence. Further, the facts derived 

 from observation of the consequences of disease or of 

 mechanical injury in man have led to the conclusion 

 that the " faculty of language " (the significant use of 

 words, not the mere production of them as sounds) is 

 especially connected with one of the frontal convolutions, 

 which is feebly represented in the apes. The convolu- 

 tions of the brain of lower races of men have not been 

 very fully studied, but the brain of a Hottentot woman 

 was long ago carefully described and illustrated, showing 

 less complexity of the convolutions than is usual in 

 European man, and making a distinct approach in this 

 respect to the apes ; but still possessing in fair proportion 

 the convolutions characteristic of the human brain. 



