THE CAUSATION OF DISEASE. 1 35 



a wide field of study here. We have seen that the spermatic 

 and germatic E cannot possibly be the same for any two germs 

 or sperms, and we have farther seen that the embryonic E is 

 capable of much diversity, and that the nature of this E exer- 

 cises an important influence on the destinies of the individual, 

 though one far less than that of the earlier germatic and 

 spermatic E. And here we may enunciate an important prin- 

 ciple, namely : the influence of E is great in proportion as it 

 acts early in the life-history of the individual. It is most 

 potent during the evolution of germ and sperm : it is more 

 potent during the earlier than during the later periods of em- 

 bryonic life : and after birth its influence grows less and less, 

 as time wears on, the diminution being most marked after 

 maturity has been reached ; for the E is then incapable of 

 interfering with development. 



The above principle follows from the fact that a small 

 initial difference will, in the course of time, lead to a very 

 wide deviation. In the germ and sperm, how inconceivably 

 complex must be the arrangement of the ultimate particles, 

 and how important, at this early date, the influence of the E 

 upon their delicate fabric ! We can well see how the slightest 

 dislocation of the ultimate germ and sperm particles will 

 modify the entii'e future development of the embryo to which 

 these two elements give origin ; and when we further reflect 

 upon the rapid and important changes occurring during the 

 earlier period of embryonic life, it is not difficult to understand 

 how influential the E is at this time iu directing the processes 

 of development in this or that direction. 



Inasmuch, then, as the ante-partem E differs for different in- 

 dividuals, it follows that all children born to the same parents 

 must differ, for a difference of E necessitates a difference 

 of structure. According to our principle of structural mean, all 

 children born to the same parents would be the same under 

 exactly the same E, save, of course, for such differences as 

 depend upon sex. But variations become an a priori necessity 

 from the diversities of E. The only point about which doubt 

 can exist is whether this diversity of E is competent to account 

 for all the differences. 



L 2 



