CEPHALIZATION 



applied it to other classes of animals. Like all great 

 thoughts, its fertility is inexhaustible and its application 

 boundless. It might be generalized as a gradually in- 

 creasing dominance of the higher over the lower and of 

 the highest over all. In this form the law is universal. 

 To give one illustration of my own : In passing from the 

 lowest protozoan to man, among the many systems of 

 organs which are successively differentiated there is an 

 increasing dominance of the highest system, namely, the 

 nervous system. Then in the nervous system an increas- 

 ing dominance of the highest part, that is, the brain. In 

 the brain an increasing dominance of the highest ganglion 

 the cerebrum. In the cerebrum, of the highest part, 

 namely, the external gray matter, as shown by the num- 

 ber and depth of the convolutions. Then among the 

 convolutions an increasing proportion in the highest lobe 

 of the cerebrum the frontal lobe, as marked off by the 

 fissure of Roland. I need hardly say that the same law 

 prevails also in the evolution of the individual, both 

 physical and psychical. As there is an increasing domi- 

 nance of mind over body, so in the mind there is an 

 increasing dominance of reflective over the perceptive 

 faculties, and finally of the moral faculties over all. The 

 same is true of social evolution. In all and everywhere 

 we find the same law of cephalization. Everywhere in 

 physical, psychical, and social evolution, in education, 

 in intellectual and moral culture, and in civilization we 

 find an increasing dominance of the higher over the lower 

 and of the highest over all. 



I do not follow up this thought only because I do not 

 know that Dana himself did so. In a singular degree 

 he united boldness of thought with extreme cautiousness 

 in method. 



Volcanism 



The third line of thought suggested to his mind by 

 his famous voyage was that of volcanism. Early in life, 



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