THE CAUSATION OF DISEASE. 227 



is to say, the individual will tend by a direct action of the E 

 upon him to become adapted to it, but seeing that, in many 

 instances, several generations of the same family do not follow 

 the same occupation, there can be no racial adaptation. 



Now many of the -occupations which the social division of 

 labour has called into existence are necessarily harmful, and can- 

 not be rendered harmless by the most careful State control. So 

 potent for evil, indeed, are certain occupations, and so diverse 

 the forms of pathogenesis belonging to them (for each par- 

 ticular occupation has its own particular set of evils attach- 

 ing to it), that it would require several large volumes to 

 adequately describe what might be well termed ' ; the occupa- 

 tion diseases." 



Nevertheless, in spite of the injurious effects of many 

 occupations, adaptation to some of them is at least theoreti- 

 cally possible. Unfortunately, the E is but too often 

 " necessarily fatal," if not to the first, at all events to the 

 second or third generation living under it. Knife-grinding 

 affords a familiar instance. In others, more or less per- 

 fect adaptation by natural selection and direct equilibration 

 may be said to occur ; but in order that this may take place, 

 it is necessary for several generations of the same family to 

 follow the same occupation. We do not, however, find this 

 occurring on any large scale. How, then, is it possible that 

 a perfect adaptation to these manifold E's should take place ? 

 It is, nevertheless, probable that the community at large 

 becomes, by natural selection, better adapted to the average 

 artificial E ; or, if not much better adapted, we must at all 

 events acknowledge that the standard of adaptation is thus 

 maintained at a certain mean ( = racial) level. 



These observations have a very wide application ; but it will 

 be sufficient for our purpose to take a few simple illustrations. 



First, let us take the case of a publican. Now, his E is 

 probably of the necessarily fatal order ; for if he does not him- 

 self succumb to it, the second, third, or fourth generation from 

 him living under it almost certainly will. Nevertheless, a per- 

 fect "class" adaptation (meaning, in this case, the "class of 

 publicans") to such an E is theoretically possible by a survival 

 of the fittest. Direct equilibration here would play no part, 



