THE CAUSATION OF DISEASE. 239 



Another construction, however, may be put upon the case ; it 

 is possible that the unfortunate wretches who were brought up 

 for trial were but a surviving few, the greater number of the 

 prisoners having succumbed to the fever, and, supposing this 

 to be the correct interpretation, we have in it a good example 

 of natural selection — the survival of those who were fittest as 

 regards a specific mal-E. 



The following is a very similar instance : " In the early part 

 of the reign of George III., a prisoner who had been confined 

 in a dungeon was taken in a coach with four constables before 

 a magistrate, and, although the man himself was not ill, the 

 four constables died from a short putrid fever ; but the con- 

 tagion extended to no others." From these facts " it would 

 appear as if the effluvium of one set of men, shut up for some 

 time together, were poisonous when inhaled by others ; and 

 possibly more so, if the men be of different race."* In this 

 case also two explanations may be offered. We may suppose 

 the prisoner to have gradually adapted himself to the dungeon 

 atmosphere, or, again, that he was one of a very few who from 

 the first were proof against it. 



A consideration of the different effects of the same contagion 

 on the human organism brings one important fact into promi- 

 nence — namely, that normality both as regards S and E is only 

 a relative expression. If an individual can live healthily in 

 any particular E, he may be regarded as normal to it, and it 

 to him When, in short, there is perfect adaptation between S 

 and E, each is normal as regards the other. A tribe of savages 

 living healthily in an ague-haunted district might, with some 

 show of truth, exclaim: " You white men are abnormal, for 

 you sicken and die in an E which is perfectly normal." With 

 equal justice the white man might retort, u No ; your E is 

 abnormal, and therefore I, who am perfectly normal, sicken 

 when exposed to it." Each statement would be correct. To 

 the savage tribe the ague-stricken E is perfectly normal, but 

 to the white man intensely abnormal.! 



* Darwin, quoted by Sir William Aitkin : "Evolution in Pathology." 

 f This question of Abnormality will be considered in Part III. 



