332 THE CAUSATION OF DISEASE. 



than does prussic acid in prussic acid poisoning. It is utterly 

 unallowable to regard the disease-producing agent as the disease 

 itself ; not only is it incorrect in point of fact, but it cannot 

 even be permitted for practical purposes, and this for two 

 reasons — first, because we cannot, in all diseases, accurately 

 define the mal-E ; and, secondly, because the same mal-E will 

 sometimes induce totally different disorders in two separate 

 individuals. Similarly, when the disease consists of a tumour, 

 some might be inclined to regard it as a separate entity, more 

 especially if the removal of the tumour should lead to a per- 

 manent removal of a series of symptoms caused by it ; but the 

 same objections apply here as in the previous case. 



What is the fundamental truth underlying the old spiritual, 

 (as we may conveniently term it) and the humoural pathology, 

 and after which they were dim gropings ? I take it to be 

 this — that they tacitly assume — and in this they agree — 

 that the essential cause of disease lies in the environment. 

 The "unclean spirit," or "devil," and the corrupt humour, 

 correspond to what I have termed the mal-E, or, more accu- 

 rately, the abnormal internal-cell-E. In both cases the evil is 

 supposed to be, not of the body — not part and parcel of the 

 body fabric — but something independent of it — an independent 

 agency, yet capable of causing disordered action in it ; for 

 although the corrupt humour was probably in all cases regarded 

 as a product of the body itself, it was evidently thought to be 

 independent of it (as, of course, was also the evil spirit, or de- 

 moniacal possession), and all efforts were, in either case, directed 

 to its removal. These primitive pathologies erred in that they 

 concentrated the attention entirely upon the E, the part 

 played by S being largely, if not altogether, left out of 

 account ; nor would there be much need to take account of 

 the S if every individual responded in exactly the same way 

 to the same mal-E ; but, inasmuch as different S's respond 

 differently to the same E, we cannot possibly neglect the part 

 played by S in causation. 



Nevertheless, the E is, in the last resort, the sole cause of 

 disease. This will be clear if we keep before us the formula 

 " S + E = disease."* If it can be shown that S is the out- 



* This formula signifies vital inter-action, whether of health or disease. 



