242 THE CAUSATION OF DISEASE. 



for the moment out of account the injurious effects of large 

 towns, we may affirm, with perfect assurance, that if two or 

 three generations engage in indoor occupations from a tender 

 age upwards, or follow such an occupation as stone-grinding, 

 which necessitates the breathing of an irritating atmosphere, 

 or, indeed, any occupation which exerts a markedly injurious 

 effect upon the body, family extinction will inevitably occur. 

 The gaps thus created are, however, eagerly filled up in the 

 fierce struggle for existence, and thus it is that, while extinc- 

 tion of individual families is ever and again occurring, each 

 class maintains its integrity, just as does a living organism : 

 fresh material is ever at hand to take the place of the cast- 

 off, worn-out products ; and it matters not to the social 

 organism whence it shall be recruited — whether it shall be 

 from persons whose parents formed part of it or not. 



I have not attempted to enumerate the many different kinds 

 of occupation which entail upon the luckless individuals fol- 

 lowing them a necessarily fatal E, for this would occupy too 

 much space ; but it is well that we should be alive to their 

 great number, and I therefore venture to recommend a serious 

 study of this question to such of my readers as have not gone 

 into it thoroughly. 



The mal-E's of which I have hitherto spoken, are such as 

 are entailed by bread-winning occupations ; but over and above 

 these there are many to which the individual voluntarily 

 exposes himself for the sake of pleasure, such as intemperance 

 in eating and drinking. These belong to the necessarily fatal 

 class of E ? s, for they must lead to family extinction if several 

 generations of the same family indulge in them from youth 

 upwards. 



Let us now briefly turn our attention to the E obtaining 

 in large cities as distinguished from that belonging to the 

 country. There is no doubt that the E obtaining in the 

 central parts of all large towns is necessarily fatal, owing to 

 the lack of sunlight and fresh air. As Mr. Oantlie observes, 

 fresh country air has not blown over the central parts of 

 London for fifty, or it may be even a hundred, years. He 

 attributes the evil results to the lack of ozone, which is entirely 

 absent from London air ; and he adds that sun-burning never 



