266 HEREDITY AND DISEASE 



tract a variation not in itself a disease (e.g. simple gastric 

 achylia) may in appropriate conditions give rise to disease. 

 Similarly, phthisis is not as such inherited ; what is inherited 

 is a predisposition to caseous degeneration of tissue and allied 

 pathological processes. 



Thus, though it may appear pedantic, and though it will 

 probably be misunderstood, we are inclined from the biological 

 standpoint to agree with the authority quoted above, that 

 " there are no inherited diseases." 



5. Predispositions to Disease 



Up to this point we have argued that mere reappearance 

 of a disease does not imply that it is inherited ; that infection or 

 poisoning before birth is quite different from inheritance ; that 

 microbic diseases should never be spoken of as heritable ; that 

 there is no warrant for believing in the transmissibility of ac- 

 quired diseases; and that, if disease means a process, the in- 

 heritance of predispositions to disease is a more accurate phrase 

 than the inheritance of disease. 



But is not this inherited " predisposition " something " mystical," 

 suggestive of the " horologity " of clocks ? 



It may be mysterious, but it is not " mystical." We may 

 not be able to picture it or define it, but it is like any other 

 germinal potentiality, except that it happens to be prejudicial 

 to the organism. It implies something out of gear in the proto- 

 plasmic machinery. 



Physically considered, life depends on an ordered sequence 

 of constructive and disruptive chemical processes, and the 

 organism is from the outset predisposed, let us say " geared," 

 to perform these in a certain routine. But the gearings are from 

 the beginning very delicately adjusted : a slight initial difference 

 may mean a life-long friction ; a slight germinal bias may deter- 

 mine the trend of the whole life. 



Among the pathological predispositions of major importance 



