530 LAWS OF MULTIPLICATION. 



feeling and thought, in a brain thus augmented in size and 

 developed in structure, is, other things equal, the correlative 

 of a greater wear of nervous tissue and greater consumption 

 of materials to repair it. So that both in original cost of con- 

 struction and in subsequent cost of working, the nervous 

 system must become a heavier tax on the organism. Already 

 the brain of the civilized man is larger by nearly thirty per 

 cent, than the brain of the savage. Already, too, it presents 

 an increased heterogeneity especially in the distribution of 

 its convolutions. And further changes like these which have 

 taken place under the discipline of civilized life, we infer 

 will continue to take place. But everywhere and 



always, evolution is antagonistic to procreative dissolution. 

 Whether it be in greater growth of the organs which sub- 

 serve self-maintenance, whether it be in their added com- 

 plexity of structure, or whether it be in their higher activity, 

 the abstraction of the required materials implies a dimi- 

 nished reserve of materials for race-maintenance. And we 

 have seen reason to believe that this antagonism between 

 Individuation and Genesis, becomes unusually marked where 

 the nervous system is concerned, because of the costliness of 

 nervous structure and function. In 346 was pointed out 

 the apparent connexion between high cerebral development 

 and prolonged delay of sexual maturity; and in 366, 367, 

 the evidence went to show that where exceptional fertility 

 exists there is sluggishness of mind, and that where there 

 has been during education excessive expenditure in mental 

 action, there frequently follows a complete or partial infer- 

 tility. Hence the particular kind of further evolution which 

 Man is hereafter to undergo, is one which, more than any 

 other, may be expected to cause a decline in his power of 

 reproduction. 



The higher nervous development and greater expenditure 

 in nervous action, here described as indirectly brought about 

 by increase of numbers, and as thereafter becoming a check 

 on the increase of numbers, must not be taken to imply 



