CHAP. VI. Tfurapcvtici. 



1. IN speaking of the general nature of disease, it has 

 been observed, that our means of analysis do not enable us to de- 

 fine in what its variation from the state of health consists: we 

 cannot say what properties are foreign, what deficient ; what com- 

 binations have taken place, what combinations it is necessary to 

 separate, what combinations it is necessary to restore, or what new 

 ones to produce, &c.; we do not know in what disease consists. 

 Yet, with this profound ignorance, we boldly employ agents of 

 various powers; and he who understands in the common way the 

 adaptation of these agents to certain cases, will sometimes succeed 

 in restoring health where death would have been the spontaneous 

 event; and will very frequently restore health in a short time, in 

 those cases in which nature would perhaps have accomplished the 

 same end by a series of lingering and protracted operations. The 

 modus operand! of medicines is what I now propose to con- 

 sider briefly. 



2. By the exhibition of medicines it is intended to change 

 the existing or diseased, and to restore the former or healthy 

 identity of the properties constituting an animal body; whether 

 these changes respect the system generally, or some individual 

 part or parts of it. The exhibition of medicines being an intro- 

 duction of foreign properties, if the cure proceeded on a direct 

 principle of causation, it must be pre-supposed that disease consists 

 in a deficiency of properties, and that those of the medicines are 

 the identical properties, the privation of which produces disease. 



3. There would be absurdity in attempting to establish this 

 as a general principle of cure: and yet there are some cases in 

 which it would be difficult to prove that this was not the mode of 

 cure. We must, however, take a general view of the facts which 

 relate to the question, if we would attempt the discovery of a 

 general principle. Mercury cures syphilis: is there any reason 

 to think that the disease which we call syphilis consists of a de- 

 ficiency of mercury, local or constitutional? Sulphur cures the 

 itch : yet we can scarcely presume that the itch arises from defect 

 of sulphur; or that fever arises from defect of antimony, because 

 *t might be cured by James's powder; or that fever consists in 



