302 HEREDITY AND DISEASE 



or it may be counteracted in amphimixis by stronger healthy 

 determinants from the other germ-cell. 



ii. Anticipation and Intensification in Disease 



Careful work in recent years has brought into prominence a 

 very interesting and important tendency in certain diseased 

 conditions. The unsoundness becomes in successive generations 

 intensified and antedated. This has been called " the law of an- 

 ticipation." According to Nettleship, anticipation in hereditary 

 disease means the manifestation of the morbid change at an 

 earlier age in each successor, either in members of each succeed- 

 ing generation as a whole or in successively born children of one 

 parentage. 



Thus a particular morbidity like the diabetic tendency may 

 come on earlier and earlier in successive generations. Thus, too, 

 a mentally degenerate stock may show earlier and earlier collapse, 

 e.g. by lack of resisting power to tubercle. 



As to the theory of this anticipation, various suggestions have 

 been made. Dr. Nettleship says : " Anticipation or antedating 

 of onset or of completion in a family might be taken to show the 

 transmission of an acquired character. But it may probably be 

 explained as well or better by assuming certain defects, taints, 

 or vices of the system, say of the blood, are not only hereditary 

 in the true or germinal sense, but able to produce toxic agents 

 in the embryo which have an evil influence upon all its cells, and 

 thus so lower their power of resistance that the innate hereditary 

 factor has freer play and is likely to manifest itself earlier. There 

 may also be toxic agents in the embryo that have no relation 

 to the hereditary vice but yet may and probably do act in a 

 similar manner as excitants of the disease." That is to say, more 

 roughly, a general and progressive degeneracy may give a specific 

 morbidity more and earlier opportunity. 



Another authority who has done much to disclose the facts of 



