THE BIOLOGY OF HEALTH 147 



potency, stalking out from the unknown, and seizing 

 a man by the throat. There may be a truth in think- 

 ing of disease as a visitation or a judgment, but a 

 great part of the vahie of the truth is lost if we do 

 not understand that disease is often an inevitable con- 

 sequence of our carelessness, or ignorance, or slug- 

 gishness, or foolhardiness. When the disciples asked 

 Christ about the man blind from his birth, " For 

 whose sin — for his own or for his parents' — was he 

 born blind ? " they were not thinking about heredity 

 or about the transmission of acquired characters, or 

 about blindness due to infection before birth, they 

 were thinking of the blindness as a judgment imposed 

 from without. That idea of disease must be given up. 

 Perhaps we get to some clearness by distinguishing 

 three kinds of diseases, considered in a large biological 

 way. These are constitutional, microbic, and modifi- 

 cational. Constitutional diseases are due to some de- 

 ficiency or exaggeration or perversion in the hereditary 

 organisation, and as the deficiency or exaggeration or 

 perversion is likely to be continued from generation 

 to generation, it is generally said that these consti- 

 tutional diseases are hereditary. It is probably more 

 accurate to say that what persists is not exactly the 

 disease, but the predisposition to the disease. As the 

 predisposition, like every other item in our inheritance, 

 requires suitable nurture if it is to be fully expressed, 

 there is some hope — and an increasing one — of letting 

 the sleeping bud sleep. The possibility is not great, 

 however, if the nurture which predisposition to the 



