THE CAUSATION OF DISEASE. 259 



in favour of this conclusion is very strong. It is true that the 

 chest measurement of the recruit has been declining of recent 

 years, but this is probably owing to the fact that more recruits 

 are now drawn from the large towns than formerly. Granting, 

 however, that the stature of the ordinarily healthy man is 

 greater now than two or three centuries ago, it by no means 

 follows that health has improved pari passu with this increase. 

 Most domesticated animals are considerably bigger than their 

 wild congeners, but they are, if anything, inferior in health 

 and vigour. Their increase in size is certainly due to better 

 diet, and good food undoubtedly tends to physical improve- 

 ment. If all our agricultural population were perfectly fed, I 

 have no doubt that, with their healthy* surroundings, a marked 

 physical improvement would take place in the course of a few 

 generations, and that health would improve in the same ratio. 

 But against the increased stature and strength resulting from 

 better food we have to set the thousand evils which accompany 

 civilization, and which tend to mitigate the advantages arising 

 from improved diet, and therefore it is that I say we must be 

 careful not to point to mere increase in stature as evidence of 

 an improved standard of health. 



How far can this levelling down process go on ? It is 

 obvious that, taking the community at large into account, it 

 cannot pass below a certain average level, and this by no means 

 a low one. We have seen that, despite the more easy E which 

 many members of civilized communities enjoy, natural selection 

 is busily at work among them. This does not permit the 

 physique and health standard to sink below a certain fairly 

 high level ; for although in a number of isolated instances 

 sickly individuals are enabled to survive, yet this, be it noted, 

 is true of isolated cases only. The community at large is 

 exposed to a decidedly rigorous E 5 nevertheless, the population 

 goes on increasing ; and we may, I think, lay down the 

 principle that a community rapidly increasing under a rigorous 

 E must have a fairly high standard of physique and health. 

 There must be a strong backbone to that community. 



* I use the wor 1 healthy here, with the qualifications contained in the last 

 chapter. 



