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afterward* a node on the tibia: we should scarcely in these (and 

 there are many such) cases assert that the disease occupying the 

 first seat was the cause of the disease occupying the second. 



4. But if one half of the body should be paralyzed by the 

 rupture of a blood-vessel of the brain ; if vomiting should succeed 

 to a blow on the head ; if disordered respiration should succeed to 

 the operation of a cause of pressure on the brain ; if atrophy should 

 succeed to disease of the mesenteric glands; if the secretion of a 

 gland should be suspended during an inflammation of it; if con- 

 vulsions should succeed the irritation of a nenre; if paralysis of 

 the sphincter of the bladder should succeed to an injury of the 

 spine, &c.: we have no hesitation in these cases in affirming that 

 the primary is the cause of the secondary affection, because we 

 know that the healthy state of the properties engaged in the 

 secondary, acknowledge the regular dependent relation,, with those 

 engaged in the primary seat of affection. 



5. Again, if vomiting should succeed the formation or (intro- 

 duction) of a calculus in the gall-duct, or to the passing of a cal- 

 culus along the ureter; or if a pain in the shoulder should succeed 

 an inflammation set up in the liver; or if hernia humoralis should 

 succeed to an affection of the urethra, perhaps produced by an 

 injection; or if tetanus should follow a punctured or lacerated 

 wound; or if pain in the breasts should succeed conception, &c.; 

 we have in these cases no hesitation in saying, that the secondary is 

 produced by the primarj change. 



6. These are examples of the classes of related disease. 

 Disease of one part, or one state of disease, might produce 

 another: 1st, by disturbing an habitual dependence; and, 2nd, 

 by the influence of an occasional cause. The first is illustrated 

 above; as if an injury of the brain should paralyze nerves whose 

 functions are dependent upon the brain, or as if respiration should 

 become laborious, or perhaps cease, by the operation of any cause 

 of pressure upon the brain, &c. The second is illustrated in those 

 other examples, in which a relation is exhibited under circum- 

 stances of disease, which was not manifested as one of dependence 

 for a natural office, during health. 



7. The affection of a dependent seat in consequence of a 

 disordered state of the seat from whence its functional properties 

 are derived, is by no means a regular occurrence. We know that 

 there might be a violent pain in the head, a throbbing of all its 

 vessels, as if the whole brain was violently disordered, and yet the 

 function of respiration, which depends upon the brain, may be but 

 little or not at all interrupted ; at the same time, a slight pressure 

 upon the brain shall impair or prevent these dependent functions. 

 The reason is, that properties are not indifferently related with 

 any cause of disorder : but their relations are precise ; as, proper- 

 ties of the brain animate the organs of respiration, these properties 

 related with the agency of pressure, not related with causes merely 

 producing pain or even inflammation; the dependent function. 



