THE CAUSATION OF DISEASE. 35 



•some other, or even all tlie other, tissues. Disease, in such a 

 multicellular organism, consists not of one, but of many, 

 morbid inter-actions, both such as occur in the tissue or 

 tissues primarily affected, and such as occur in those secondarily 

 affected by the secondary mal-E's. 



We have hitherto said nothing as to the causation of S, but 

 have engaged ourselves with the E. We have seen that in 

 multicellular organisms this falls under two heads : the 

 internal and the external E, and that the latter is far 

 more complex than appears at first sight. Space did not 

 permit a minute analysis of the external-body-E, but enough 

 was said to show its complexity, both in its mental and its 

 physical side. It is with the physical E that the physician 

 has more particularly to do. It is his business to dis- 

 cuss what forms of E are good for the physical well-being 

 of man and what are hurtful, just as it is the business of 

 those responsible for his mental welfare to seek out the good 

 and bad forms of mental E ; and it is a very happy fact 

 that our external-body-E, both mental and physical, is very 

 largely under our control. 



If an individual have no tendency to disease — if, that is 

 to say, his S is perfect, and if he pass from infancy to man- 

 hood under a perfect external-E — the vital processes will 

 go forward in orderly fashion: there will be health. Given 

 a healthy body, evil can only come through E; and indeed, 

 as we shall see, all disease originates, on final analysis, 

 through E, and through E alone. And just as evil can only 

 come through E, so it is through E alone that we can exert 

 a beneficial influence on cell-action. In practical medicine 

 this is done by enforcing the principles of hygiene and by 

 administering drags. The wise physician well knows upon 

 which he places most faith. 



D 2 



