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skm may be destroyed by boiling water, by a hot iron, by the 

 flame of a candle, by melted lead, by a heated coal, by boiling oil, 

 &c.; these appear different causes, that is, the efficient cause, vix. 

 heat, is differently allied. 



$ 5. But, iu the cases of disease, the analogy to these latter 

 instances does not obtain: a disease consists either of defective or 

 of foreign properties compared with the state of health; if it is 

 only one of these, or both (and there is no alternative), the cure, or 

 restoration of health, must require either that the deficient proper- 

 ties be supplied or the foreign ones removed, or both; here again 

 there is in the efficient causation no other alternative. But the 

 cure by remedies is accomplished in contradiction to these modes, 

 and therefore these modes, which are the only ones of direct causa- 

 tion, cannot be the modes by which remedies act : thus, suppose 

 our pain in the head to arise by defect of the tonic power of the 

 arteries, by which a preternatural dilatation is admitted, emetic 

 tartar and aloes will cure this defect of tonicity: if they do it by 

 supplying the tonic power which was deficient, how happens it that 

 leeches, or bleeding from the temporal artery, both of which 

 abstract blood, and do not supply deficient properties, will also 

 produce the same effect? or, suppose the pain in the head to be 

 produced by some properties deficient and some foreign, a bleeding 

 from the head can be supposed with the greatest latitude of as- 

 sumption only to remove properties which are foreign to the state 

 of health. Yet the disease ceases, leaving the supply of the de- 

 ficient properties unaccounted fpr. 



6. It is sufficiently plain from these considerations (and in- 

 deed by a little further discussion, which seems superfluous, it 

 might be demonstrated) that the general operation of remedies is 

 not by supplying deficient, or removing foreign properties, in the 

 direct or efficient mode of causation, as if disease of the bowels 

 consisted in a deficiency of some properties which exist in rhubarb, 

 &c. but that these properties produce their effects by an indirect 

 causation. 



7. We find that this inference, deduced in conformity with 

 our minuter reasonings, is equally supported by the palpable effects 

 of remedies: so far from unchanging the diseased, and restoring 

 the healthy state by the communication, or the removal of precise 

 differential properties; so far from this, all the remedies which 

 have a sensible operation are themselves, as is well known, the 

 causes of disease, or all tend to produce preternatural conditions. 

 This effect will be recognized by enumerating a few of the reme- 

 dies chiefly relied on : such as mercury in its various forms, aloes, 

 scammony, jalap, colocynth, elateriuni, gamboge, neutral salts, 

 senna, antimony, ipecacuanha, squill, digitalis, nitre, assafoetida, 

 bleeding, blisters, warm bath, opium, brandy, wine, ammonia, 

 aether, arsenic, hemlock, c.; all these remedies which have sensi- 

 ble effects are not the direct causes of health, but of diseased 

 states. If, then, an agent, whose direct operation is to produce 



