312 



that remedies of this kind, curing by repeated doses, the direct 

 causation might obtain, and yet the state of health not be im- 

 mediately restored because the quantity was deficient. This answer 

 is, however, invalidated by the additional fact, that if the quantity 

 is increased, so far from improving the effect, it may produce death, 

 as arsenic, for example, which nevertheless cures by a repetition of 

 small doses. The perceptible effect, also, of most remedies of this 

 kind is to produce a state different from health: they cannot there- 

 fore on this account be admitted to operate in the direct way. The 

 inference is therefore warranted, that medicines which operate by 

 latent causation, do it by a process the result of which is attained by 

 intermediate relations. 



10. The subdivisions of the third class, or of remedies which 

 operate by latent causation, are, 1st, those that cure without a sensi- 

 ble operation; 2nd, medicines that produce cure by sensible change, 

 or by sensible effects; 3rd, medicines that cure by employment 

 upon the seats of disease, with or without sensible effects; 4th, 

 medicines that cure by an operation upon related seats, with or 

 without sensible effects. To speak now more particularly of the 

 relation which each of these classes has with the condition of disease. 



1st, Medicines that operate without sensible effects. In this 

 manner arsenic may cure intermittent fever, scorbutic disease, &c. 

 In this way diseases are cured by bark, by antimony, and mercury, 

 in small doses, &c. The cure in these instances is accomplished by 

 successive causation, and consequently the relation of the remedy 

 with the condition of the disease is mediate. 



2nd, Medicines that cure, producing sensible effects or disorder 

 of their own. The remedies which fall under this class are by far 

 the most numerous: to this class belong all the emetic and purga- 

 tive medicines, arsenic and mercury, in large or frequent doses, 

 antimony, steel, henbane, hemlock, digitalis, blisters, bleeding, 

 issues, &c. These remedies also operate by successive or inter- 

 mediate causation, without removing, in the cases we are supposing, 

 known causes. 



3rd, Medicines that cure by employment upon the seats of the 

 disease. In this way all those remedies act which are applied to 

 individual seats through the medium of the circulation. In this way, 

 also, the topical remedies act, such as cupping, lotions, blisters, &c. 

 These operate by mediate relations; and in the cases we are sup- 

 posing, that is, where the precise cause of disease is not ascertaina- 

 ble, by a train, or succession of latent processes of causation. 



4th, Medicines that cure by an employment upon related seats. 

 Thus, a disorder of the head is cured by emetics, or anasarca of the 

 legs by purgatives; or a disorder of the head existing beneath the 

 cranium, by the actual cautery to the scalp ; or a disease of the eye, 

 by an issue in the arm or a seaton in the back of the neck; or as a 

 disorder of the stomach is cured by purgatives, or an inflammation 

 of the pleura by blistering the skin; or as a disease of a joint is cured 

 by a caustic issue, &c. These remedies act also by successive 



