INNATE AND ACQUIRED DISEASE 257 



children were deaf ; where one parent was adventitiously deaf 

 and the other normal, the percentage was 2-244. I n short, there is 

 no evidence that adventitious deafness is heritable at alL 



It may be noted further that Fay's statistics show that deafness 

 among the relatives of the parents increases very markedly the 

 likelihood of there being deaf children ; and they also seem to show 

 that consanguineous marriages greatly increase the probability of 

 the inheritance of deafness, or of constitutional conditions, e.g. 

 lymphoid exaggeration, such as naturally lead to deafness. This 

 is what would be expected from the fact that an individual in- 

 heritance is a mosaic of ancestral contributions. 



The position we venture to maintain is expressed in the 

 following sentences : — " As inherited (on the part of the off- 

 spring) or transmitted (on the part of the parents), Biology 

 includes only those characters or their physical bases which 

 were contained in the germ-plasm of the parental sex-cells " 

 (Martius, 1905, p. 11). Similarly, Virchow says : " What 

 operates on the germ after the fusion of the sex-nuclei, modi- 

 fying the embryo, or even inducing an actual deviation in the 

 development, cannot be spoken of as inherited. It belongs 

 to the category of early acquired deviations, which are therefore 

 frequently congenital." This pronouncement is the more re- 

 markable since Virchow believed in the inheritance of acquired 

 characters. 



Is the Distinction between Innate Disease and Acquired 

 Disease Practicable ? — It is true that the distinction between 

 an " innate " predisposition to a disease and an acquired 

 disease " looks better on paper than by the bedside." This 

 is simply an instance of what we continually find, that the 

 " abstract " theoretical concepts of science are not always 

 readily applicable to the intricacies and subtleties of nature. 

 And yet the distinction is quite legitimate and thoroughly 

 sound and useful in the present state of our knowledge. We 

 cannot object to the utility of abstracting an " organism " 

 from its " environment," although we know that a living 



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