268 



SCIENCE. 



[N. S. Vol. VII. No. 165. 



multiplied by such agencies as steam and 

 electrical machines, etc. , in the same man- 

 ner. The printing press is an extra-organic 

 memory far more lasting and durable than 

 the plastic but fickle brain. Fire provides 

 man with a second digestive apparatus by 

 means of which hard and stringy roots and 

 other materials for food are rendered di- 

 gestible and poisonous roots and herbs ren- 

 dered innocuous. Tools, traps, weapons, 

 etc., are but extensions of bodily contriv- 

 ances. Clothing, unlike the fur or layer of 

 blubber of the lower animal, becomes a 

 part of the organism at will. One becomes 

 more or less independent of seasons, cli- 

 mates and geographical restrictions. Thous- 

 ands of extra-organic adaptations are being 

 invented (most of them really accidental 

 variations) every day. 



Professor J. Mark Baldwin, writing on 

 this question of social heredity, de- 

 fines it as ' the process by which the 

 individuals of each generation acquire the 

 matter of tradition and grow into the habits 

 and usages of their kind.'* Hy social hered- 

 ity I mean not only this, but also the trans- 

 mission from the parents to the children of 

 the improved environment, more especially 

 of the extra-organic sense and motor organs. 

 By organic heredity I mean, roughly speak- 

 ing, the transmission of the congenital char- 

 acteristics of the parents to the children. 



By the latter process alone, all progress 

 depends upon the transmission of variations 

 occurring loitliin the organism. Thus prog- 

 ress would be, as it has been, indefinitely 

 slow. Moreover, these advantageous or- 

 ganic variations die with the individual, and 

 must be born again, so to speak, with each 

 new individual. This requires time. On 

 the other hand, by means of social heredity 

 each new member of the race has handed to 

 him at birth, not only the accumulated or- 

 ganic advantageous variations of sense and 



* Science, April 23, 1897. See also Lloyd Mor- 

 and Instinct, pp. 340-343. 



motor organs (animals and the poor inherit 

 in the same way !), but has handed to him 

 the extra-organic adaptations which have 

 multiplied so indefinitely in the age of civi- 

 lized man. The vast importance of accu- 

 mulation of capital is obvious. 



In this way man's organism is indefi- 

 nitely extended. He reads Aristotle, and 

 his organism reaches back two thousand 

 years. He reads the latest cable from Aus- 

 tralia and Japan, and he listens at the 

 antipodes. With an electric button he ac- 

 complishes herculean tasks. There are 

 giants in these days. 



The extra-organic part of his organism 

 becomes in many cases as valuable to man 

 as his organic part. Ofttimes for it he will 

 sacrifice his life, as the soldiers throw 

 their lives away on the battlefield to save 

 the gun. 



This is obvious and well-known. Such 

 large requirements meeting the individual 

 on the threshold of his life demand a large 

 measure of plasticity. Adaptability to one's 

 new environment is always the mark of 

 high intellectual development. Such adapta- 

 bility is rendered possible by the nature and 

 growth of the brain. Of the 800 to 1,000 

 million nerve cells present in the human 

 cortex, all are formed before birth. But all 

 are not developed. Cell elements are pres- 

 ent but immature, mei-e granules, nuclei 

 which do not form a functional part of the 

 tissue. Under certain conditions, however, 

 they are capable of further development. 

 With further growth and exercise nerve 

 fibres appear and form functional sys- 

 tems. 



It seems, therefore, that in addition to 

 the cells and fibres connected at birth (and 

 sometimes later), as in instincts, there is a 

 mass of latent or potential nerve cells and 

 fibres which await connection. These form 

 probably the physical basis of our acquired 

 (mental) characteristics. 



Thus there is rendered possible the speedy 



