Heredity and Education. 333 



crease in size, at least those that are functional, about a thou- 

 sand times ; but the main bulk of the brain at all times consists 

 of axones and dendrites — the telegraph wires ; so this increase 

 in size of the cells through use does not greatly increase the 

 size of the brain, that of the adult weighing about three and 

 one-half times as much as the brain of the child at birth. 



The stages in the evolution of man's brain are likewise shown 

 in the brains of his fellow vertebrates which were left behind 

 in the race for greater efficiency. The nervous system of the 

 lancelet is merely a tube. The brain of the fish, amphibian and 

 reptile consists of the basic ganglia with a small cerebrum. In 

 birds the cerebrum, for the first time among vertebrates, ex- 

 ceeds the other basic ganglia in volume. Among lower mam- 

 mals the cerebrum so much exceeds the other basic ganglia in 

 size that it covers the optic ganglia on the rear and the ol- 

 factory^ lobes in front. Furthermore the cerebrum of modern 

 mammals far exceeds in size the same ganglion in mammals of 

 the same size that lived two million years ago. In man the 

 cerebrum reaches its culmination in size and covers all the 

 basic ganglia, including the cerebellum. 



No reason is known to the biologist for this increase in size 

 and complexity of the brains of vertebrates from the lowest to 

 the highest and through the periods of geologic time, except 

 that they used their wits more and more in their struggles for 

 existence, the brain culminating in size and complexity in man. 

 As the chief growth in size of the cerebrum is in the front and 

 rear portions, those parts whose functions are largely conjec- 

 tural, it would seem to be entirely safe to assume that the 

 thought centers, the wit centers, are located largely in these 

 portions. But normal children possess ail these centers at birth ; 

 they are merely undeveloped. The nerve cells must take nutri- 

 ment, increase in size, and grow a more complex system of as- 

 sociation fibers. The activities of the mind stimulate the 

 growths of the brain, just as the activities of the body cause 

 special developments of its organs. 



It should not be assumed, however, that the growth of mind 

 and brain are unlimited, for heredity says, in many cases, thus 

 far ard but little farther. Doctor Goddard of Vineland, N. J., 

 found in his institution for the feebleminded that idiots 

 stopped developing mentally at two or three years, in spite of 

 best efforts of teachers; imbeciles at seven, and morons at 



