303 



is a parallel argument, viz. gout in the bead is produced by disor- 

 der of the feet, or pleurisy is produced by a state of the skin 

 covering the side, because agents applied to these parts will cure 

 diseases occupying other seats. Nothing can prove causation 

 between diseases where the succession is not clear; and even where 

 the succession is clear, this must be admitted as a proof only, with 

 the restrictions before mentioned. 



33. But, it will be further insisted, in those diseases which 

 blue pill cures, the stools are black, the secretions depraved, &c. 

 This fact, singly, proves only associated, or concomitant disease in 

 different seats. " If upon a spontaneous evacuation of similar mat- 

 ter from the bowels connected disease should cease, according to 

 the only rules of reasoning which can be defined, we are then to 

 infer an example of that class of related disease which is by sub- 

 stitution; that is, the disease elsewhere is cured, according to such 

 evidence from symptoms, by disease of the abdominal viscera. 



34. That disease of the stomach, liver, &c. may, as well as 

 any other parts, become the seats of related disease, whether 

 of substitution or of extension, cannot be denied. Indeed, in our 

 sketch of an illustration of related disease, this degree of impor- 

 tance has been assigned to these viscera: thus, an excessive irrita- 

 bility of the retina which existed for years, while the health was 

 in every other respect good, has been cured by a spontaneous 

 chronic diarrhrea; and of the class of simple extension, thus, a 

 local disease, say in order jto avoid a cavil an artificial one, as a 

 gun-shot wound, with diseased bone, may impair the appetite and 

 totally disorder the functions of the abdominal viscera : this 

 disorder began perhaps in the leg; it may be extended to the brain 

 and nervous system; or it may be extended from this system to 

 that of the preparatory organs, and, fvom disorder of these organs 

 in an adequate degree, the disorder may be extended more or less 

 to the whole system. This js the greatest share which can be al- 

 lowed to these organs in the complexity of disease: they may be- 

 come the seats of related disease, this may be disease either of 

 substitution or of extension, and these organs may, in common 

 with other parts, become the seats either of primary or of secondary 

 disease. But, as the seat of an universal origin of disease, the 

 notion can be supported only by arguments which will scarcely 

 bear the slighest examination, and which may with the greatest 

 ease be refuted, even though arguments of a similar description 

 should be multiplied a hundred fold. 



35. The discussion here pursued with respect to the nature 

 of related disease, may be nearly comprised in a summary of the 

 following kind: 



1. By related disease is implied conditions of the properties 

 of a seat which produce effects, either curative or not, in the way 

 of causation. 



2. Causation between phenomena in animal bodies is inferred 

 from succession in a sufficient number of instances, either of the 



