7§ THE CAUSATION OF DISEASE. 



of them to give a more or less exact mean ; but here the com- 

 plicated question of pre-potency comes in. If the father's 

 nose be aquiline, that of the mother being retroussee, one 

 would rather expect the nose in the offspring to be some 

 sort of mongrelized product of the two. But this is not neces- 

 sarily the case : either kind of nose may be inherited un- 

 changed. It is well known, as already mentioned, how tena- 

 ciously an aquiline nose will cling to a family. Why such' a 

 character should be pre-potent it is difficult to say. Possibly 

 one element in causation may be the ancestral age of the pre- 

 potent character. One would expect a character which had 

 constantly belonged to a race for many generations to have a 

 greater propagating power than one recently acquired. I 



"imagine, for instance, that in the mulatto (half white and 

 half negro) the flattened nose of the negro, which has belonged 

 to the race for thousands of generations, would gain the 

 ascendency. I only mention this influence of ancestral age as 

 one possible element in the causation of pre-potency. 



It sometimes happens, however, that unlike Mendings of 

 the same tissue give a compound quite unlike the two elements, 

 just as the compound of two chemical elements may be quite 

 unlike either of them. "Who can say, for instance, what will be 

 the exact result of two peculiar mental blendings ; the diversity 

 among mental characters is so enormous, and the nature of the 

 acting forces so subtle, that we can well understand how their 

 several blendings may yield mental traits whose parentage we 



.are quite unable to trace. The like is true of other proper- 

 ties. Now, in such cases it may be said that the product 

 is not inherited ; nor is it in the sense that the same peculiarity 

 is inherited, bat strictly speaking it is inherited, inasmuch as 

 each element is derived from the parents. 



The coming together of unlike physiological characters of the 

 same tissue may give a curious result — one which is in no sense 



.a blending — and may similarly lead us to suppose that the char- 

 acter resulting from their union is not inherited, though such is 

 actually the case. If, namely, the two characters be of recent 

 ancestral acquisition, it may happen that they are dropped in the 

 offspring, which lapses to a status quo ante the acquisition of 



. these characters. This reversion, for such it is, does not occur 



