THE CAUSATION OF DISEASE. 293 



abnormal to others, and this is true of many other similar E's. 

 Many individuals, for instance, are incapable of being in- 

 juriously affected by the poisons of the specific fevers, and, so 

 far as such individuals are concerned, the presence of these 

 around and about them does not constitute abnormality of E. 

 Who knows, indeed, how many unseen agencies there may not 

 be about us, which, in days gone by, were capable of working 

 great ill upon our race, but which, by adaptation through the 

 course of long ages, have come to be quite innocent — agencies 

 which once constituted an abnormal E, but which are now 

 quite normal. And what is true of the poisonous products of 

 micro-organisms is doubtless true of innumerable simple forms 

 of E. The homely saying, ,: What is one man's meat is another 

 man's poison," bears witness to the truth of this. To some, 

 for instance, ordinary quantities of alcohol are quite harmless 

 — nay, they may even be beneficial ; to others — e.g., the rheu- 

 matic and gouty — they are actually poisonous. In the first 

 case, S and E permit the vital processes to proceed healthily : 

 each is normal as regards the other. In the second case, 

 unhealthy action results : each is abnormal as regards the 

 other. 



Let us now turn to some of the more complex forms of E. 

 Those of which we more particularly spoke just now are of 

 the simplest kind, consisting, in fact, of a simple agent — 

 namely, some animal or vegetable substance. The E of an 

 individual, however, consists of the sum total of influences 

 (mental and physical) operating upon him, and hence it follows 

 that E is infinitely complex and diverse. A long chapter 

 would be needed to illustrate the complexity and diversity of 

 man's E. My purpose, for the moment, is to call attention 

 once again to the diversity of E in a civilized community more 

 especially. In a primitive community the E is very much 

 alike for all, but as the division of labour proceeds in the 

 social organism, we have in the same community a multiplicity 

 of environments, for each separate occupation has an E peculiar 

 to it. It were a long task to tell in detail how the E's of 

 particular occupations differ, but it will be readily granted that 

 they do differ. Compare the surroundings of the soldier, 

 sailor, scholar, peasant, miner, butcher. The great difference 



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