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duced by primary attacks, these predispositions and insuscep- 

 tibilities often amount to constitutional peculiarities in 

 which, somehow, heredity must have had a share in 

 producing. If they appear to be the result of variability, 

 it must be remembered that variability is necessitated by 

 evolution, and without heredity, evolution, nay, life and varia- 

 tion are impossible ; for " evolution produces physiological 

 and psychological modifications ; habit fixes them in the 

 individual, heredity fixes them in the race ;" so that heredity 

 and variability act and interact inseparably through the 

 universal kingdom of organic life and being. Thus alike in 

 races, families, and individuals, does heredity assert itself, 

 and thus are races, families, and individuals, preserved and 

 perpetuated, differentiated and destroyed by heredity and 

 variability, and as in health, so likewise in disease. 



I have still, however, to consider the diseases of the organs 

 of special sense, and also those of the skin. To some of 

 the former I have already alluded in an earlier portion of 

 these papers, when discussing the heredity of sensorial 

 qualities, but as this allusion was from the psychological 

 stand-point, I may now be permitted to refer more par- 

 ticularly to the same, only from a pathological point of 

 view. I then showed that besides those varieties of vision 

 depending upon mechanical causes, those also depending 

 upon anaesthesia or hyperaesthesia of the nervous element 

 were all hereditarily transmissible. Of those dependent 

 upon mechanical causes, strabismus, myopia, and presbyopia 

 are the most common, and these are all markedly hereditary. 

 Portal describes the Montmorency sight an imperfect form 

 of strabismus which distinguished nearly all the members 

 of that family. Stahl also relates the following remarkable 

 case : A soldier lost in war one of his eyes. He returned 



