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physicians admitting the class of facts, and admitting also the in- 

 ference of a relation, believe that the examples are very rare; others 

 are inclined to think them universal, aye, and to allow them only 

 one tendency, although they might tend to 50, or 500 different 

 effects. It will appear from this account that the existence of 

 related disease has been long known, that the knowledge of it has 

 become popular, and consequently there is no novelty in the state- 

 ment of the fact. If we would improve our knowledge with 

 fespect to such disease, it must be, not by ignorantly generalizing a 

 single limited class, but by a just analysis of its laws, by an in- 

 quiry into its nature, its frequency, and by an accurate discrimina- 

 tion of its instances. The first subdivision which we have proposed 

 of this class is that of related secondary disease, tending to cure, 

 the primary. 



6. Perhaps the most unequivocal examples of related secon- 

 dary disease, tending to cure that which occurs in a primary seat, are 

 those of metastasis. A person might have pneumonia clearly charac- 

 terized by its symptoms: the symptoms of this local disease on a 

 Sudden shall cease, and the subject become immediately affected 

 with phrenitis, which shall be followed by death within eight and 

 forty hours. These occurrences may be confirmed after death by 

 dissection (quod Vidimus testamur). If we inquire into the causation 

 in this example, Were are those to whom the whole process is per- 

 fectly clear, who will reply, the inflammation left the lungs and went 

 to the brain; was it then the same inflammation, and if so, what was 

 the object of its journey, or why did the inflammation take it into 

 its head to travel ? To analyze a little more curiously : 



7. Inflammation exists in the lungs: why does it cease in the 

 lungs? either from that progressive causation (which has been d- 

 scribed) taking place in the lungs, or from a progressive causation 

 taking place elsewhere, by which a relation is opened between the 

 seat of such progressive change and the properties engaged in tht 

 disease of the lungs, the end of which relation is, that disease is 

 established in a secondary, and ceases in the primary seat. 



8. The evidence in this case derived from the order of suc- 

 cession is, that the disease in the lungs being the antecedent, is also 

 the cause of the disease in the brain which succeeds to it; in other 

 words, the properties constituting inflammation of the lungs leave 

 this seat and are transferred to the brain. But if the pneumonia is 

 the antecedent to the phrenitis, what is the antecedent to the metas* 

 tasis? or why does a disease leave a seat in which it is established I 

 The alternatives which must form the answer to this question are 

 suggested above : either a change takes place in the properties of 

 the lungs, by which they no longer admit the state of inflammation, 

 which is then assumed by some other viscus, already in a predisposed 

 state to take up inflammation upon the cessation of it in another 

 seat; or else the brain (continuing our example) assumes a state 

 which is so related with the properties engaged in the inflammation 

 f the lungs, as to produce a cessation of the inflammatory condition 



