CHAPTER XVI. 



The Influence of Environment upon Structure — The Influence of the Ante- 

 partem Environment (continued) — Differences in E the Prime Cause of 

 Natural Variations. 



We have already seen that the E is not so effective after birth 

 as before it. Nevertheless, from a health point of view, it is 

 of far greater importance, because there is greater room for 

 morbid influences after birth, when the E abounds in evils. 

 Moreover, before birth the organism is, in a sense, parasitic, 

 but after birth it becomes independent and capable of regu- 

 lating its own E. 



Indeed, although the post -partem E is less able to influence 

 S than the ante-partem E, owing to the great plasticity of the 

 embryo, it is nevertheless a fact that the post-partein E is 

 capable of inducing very considerable structural change, the 

 growing complexity of the E as the individual waxes older 

 being to some extent a set-off against the lessening plasticity 

 of his tissues. If the E of different individuals must be 

 unlike before birth, how much more unlike must it be after 

 birth ! The complexity and necessary diversity of the post- 

 partem E was insisted on in a former chapter. We there saw 

 how, in a complex society, the number of different E's in- 

 creases as the division of labour proceeds, for the E differs 

 in every occupation. And thus it happens that, if all people 

 came from their mother's womb exactly alike, they would 

 soon begin to differ in a recognizable way. Let one of 

 twins become a soldier, the other a shoemaker, and we shall 

 have no difficulty in telling the one from the other, no matter 

 how great their original likeness. And not only will they 

 be altered in obvious bodily structure, but a careful look 

 into the mental world of each will disclose a marked 

 difference there alsOv Thus do our surroundings mould 



