608 



SCIENCE. 



[N. S. Vol. XIV. No. 355. 



an eminence, we may reasonably conclude 

 that the growth in the area concerned is the 

 structural foundation of what will become 

 later on a center of functional activity of 

 an acute kind. 



A consideration of this matter gives the 

 clue to the simple convolutions of the ape 

 and the complex convolutions of man, and, 

 further, it explains how the interrupted 

 form of fissural development is one of the 

 essential characteristics of the human brain 

 as compared with the simian brain. Areas 

 which rise up in the form of one long ele- 

 vation on the surface of the ape's brain ap- 

 pear in the form of several eminences on 

 the surface of the human brain, and fissures 

 which appear in the form of long continu- 

 ous slits in the simian cerebrum appear in 

 the human cerebrum in several detached 

 bits, which may or may not in the course 

 of time run into each other and become 

 confluent. All this is due to the greater 

 definition, refinement and perfection of the 

 functions carried on in the cerebral cortex 

 of man. It is an index of a more complete 

 ' physiological division of labor ' in the 

 human brain. 



It is not necessary, for the purpose I 

 have in view, to enter into any detail re- 

 garding the many points of difference 

 which become evident when the cerebral 

 surface of the ape is compared with that 

 of man. It is more my purpose to indi- 

 cate certain of the districts of cerebral 

 cortex which have undergone a marked 

 increase in the human brain — an increase 

 which may be reasonably supposed to be 

 associated with the high mental attributes 

 of man. To us, at the present time, it is 

 difficult to conceive how it was ever pos- 

 sible to doubt that the occipital lobe is a 

 distinctive character of the simian brain as 

 well as of the human brain, and yet at suc- 

 cessive meetings of this Association (1860, 

 1861 and 1862) a discussion, which was 

 probably one of the most heated in the 



whole course of its history, took place on 

 this very point. One of our greatest au- 

 thorities on animal structure maintained 

 that the occipital lobe and the hippocampus 

 minor — an elevation in its interior — were 

 both peculiar to man and to him alone. 

 Every one has read in the ' Water Babies ' 

 Charles Kingsley's delightful account of 

 this discussion. Speaking of the Professor 

 he says: '^He held very strange theories 

 about a good many things. He had even 

 got up at the British Association and de- 

 clared that apes had hippopotamus majors 

 in their brains just as men have. What a 

 shocking thing to say ; for if it were so, 

 what would become of the faith, hope and 

 charity of immortal millions? You may 

 think that there are other more important 

 differences between you and an ape, such 

 as being able to speak, and make machines, 

 and know right from wrong, and say your 

 prayers, and other little matters of that 

 kind ; bufe that is a child's fancy." In the 

 light of our present knowledge we can fully 

 understand Professor Huxley closing the 

 discussion by stating that the question had 

 'become one of pei"sonal veracity.' In- 

 deed, the occipital lobe, so far from being 

 absent, is developed in the ape to a rela- 

 tively greater extent than in man, and this 

 constitutes one of the leading positive dis- 

 tinctive characters of the simian cerebrum. 

 Measured along the mesial border, the per- 

 centage length of the occipital lobe to the 

 total length of the cerebrum in the baboon, 

 orang and man is as follows : 



Baboon 29.7 



Orang 23.2 



Man 21.2 



But these figures do not convey the full 

 extent of the predominance of the occipital 

 lobe in the ape. The anterior border of the 

 lobe grows forwards beyond its proper lim- 

 its, and pushes its way over the parietal 

 lobe which lies in front, so as to cover over 

 a portion of it by an overlapping lip termed 



