THE CAUSATION OF DISEASE. ?g 



if the characters are in the same direction, but only when 

 they are unlike. These unlike characters refuse to combine, 

 and the offspring inherits a structural condition belonging to 

 an ancestral period antecedent to the acquisition of such char- 

 acter. This subject will be considered again hereafter. 



These considerations show how difficult it is to foretell what 

 will be the result of the union of unlike physiological characters. 

 For, first, one of the combining elements may be pre-potent ; 

 or the two may fuse into a more or less exact mechanical mean 

 (as in the case of features, size, &c.) ; or again, the resulting 

 compound may be unlike either component element; finally, 

 the two characters may refuse to blend altogether, both dis- 

 appearing, and revealing a character of earlier ancestral date. 



It will be long before we can lay down precise rules 

 which shall enable us to predict the effect upon the offspring of 

 different parental unions. This could only be done by observ- 

 ing the actual results of different unions. We should 

 probably, however, be for the most part correct in predicting 

 pre-potency of a character in those cases where its ancestral 

 age is much greater than that of the other blending element ; 

 and, on the other hand, a total disappearance of each character, 

 with reversion, where both are of recent ancestral origin and 

 divergent nature. Little more can be said in the shape of 

 general statements. 



ic. The blending characters are normal, and belong to 

 different tissues. This, strictly speaking, falls under the last 

 head, and therefore needs no further consideration. 



In regard to the blending of unlike physiological characters, 

 an interesting question arises — viz., Is it possible for two 

 physiological bl endings to lead to a pathological result? 

 Suppose A. and B. to be healthy men, and C. a healthy 

 woman. Is it possible that while the children of A. and C. 

 are healthy, those born of C. by B. shall (cwleribus paribus) 

 be unhealthy ? This may seem an astounding question, but 

 it is one deserving our serious thought. In a healthy 

 organism there is, in the language of Spencer, equilibrium 

 between the inner and outer relations. The living organism 

 is what he would call a moving equilibrium — that is to say, 

 it consists of an inconceivably complex array of forces, which 



