262 HEREDITY AND DISEASE 



and of modificational origin, where it is really an acquired condition, 

 there is no warrant for believing that it is transmissible. 



OTHER CASES. It proves nothing to cite instances of myopia 

 appearing in adolescence and reappearing in the early life of the 

 offspring ; of neuroses manifested after an accidental shock in the 

 parent, but patent from the^first in the child ; of rupture manifesting 

 itself in the parent after an abnormal strain, and occurring without 

 apparently adequate cause in the next generation, and so on. It 

 is always possible, and indeed reasonable, to answer that we have 

 in such cases to deal with an inherited germinal predisposition. 



Cardiac hypertrophy due to over-work is in a sense a diseased 

 condition, though from a wider point of view it may be said that 

 the organism is here, as always, doing its best in the way of adaptive 

 response to novel conditions. But is there any warrant for sup- 

 posing that cardiac hypertrophy in a father will induce cardiac 

 hypertrophy or even a tendency to it in his son ? " Of course, 

 the constitution that made the father liable to hypertrophy would 

 also make the child liable, but this is inheritance of a constitutional 

 (non-acquired) character a thing no one disputes " (Dr. Leslie 

 Mackenzie, Scot. Med. Surg. Journ. vi., 1900, p. 324). 



Those who accept the concept of a germ-plasm of unimagin- 

 able intricacy, persistent with remarkable dynamic inertia from 

 generation to generation, changing and yet stable, oscillating in 

 parts and yet on the whole "breeding true/' will not lightly 

 assume that modifications in the body can bring about a specific 

 change of structure in the germ-plasm. It is possible that 

 profound bodily changes, such as some acquired diseases effect, 

 may shake the kaleidoscope and provoke a change to a new 

 position of organic equilibrium; but it does not seem likely. 

 On the other hand, important bodily modifications, e.g. serious 

 derangerrents due to infectious diseases, may effect a change 

 in the vigour (functioning-power, growing-power, developing- 

 power, resisting-power) of particular elements in the inheritance. 

 And this admission is probably enough to cover all the well- 

 authenticated cases of inborn changes in the offspring of parents 

 who had acquired serious diseases. 



