334 THE CAUSATION OF DISEASE. 



and female — to be born into the world exactly alike, save for 

 sexual differences. We know that in course of time each will 

 diverge in structure, owing to the necessary differences in the 

 E. Let us represent these structural differences, or acquired 

 characters — say, at the age of twenty-five — by the symbols s,, 

 s., respectively. Then, if S represent those structural characters 

 of each individual which are the pure outcome of heredity, Ss x 

 and Ss., will represent the structure of each at the above age, 

 when differences of E have had time to affect it. If the two 

 individuals now come into sexual union, they will be a cross in 

 respect of Sj and s.„ and the coming together in the offspring 

 of these two different tendencies will lead to a condition which 

 may be represented by Ss ? — the offspring differing from the 

 parents in respect of s ? . Now, seeing that the structural 

 differences represented by Bj, s., have been wrought through 

 the E, may we not justly conclude that s ? , which is a product 

 of the two, has a similar origin ? Each ingredient in a com- 

 pound being the result of E, is it not true that the compound 

 itself has a similar origin, even though it be quite unlike 

 any of its ingredients ? Let us suppose that in a world where 

 and H do not exist, each is called into being by a particular 

 agency, at such a temperature that the two fly together to form 

 water ; should we not attribute to this agency a preponderating 

 share in the causation of water ? and similarly, if we grant that 

 the S of two individuals coming into sexual union is ultimately 

 due to E, we must grant that the S of their offspring is 

 due to E, even though the offspring may manifest structural 

 characters not present in either parent. 



It is therefore, I think, clear that, directly or indirectly, all 

 modifications of S come through E, and since organic evolution 

 results from the accumulation during countless generations of 

 individual modifications, we see that the causation of S in its 

 entirety is ultimately traceable to E. Wherefore the material 

 conditions represented by S and E are solely due to E, and as 

 this formula represents not only healthy vital inter- action, but 

 also unhealthy inter-action — i.e., disease — it follows that all 

 disease ultimately comes through E. 



But lest any one should still maintain that such structural 

 states as depend upon the coming together of unlike parental ten- 



