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it can exist, viz. in the condition of the part which is the seat of 

 the affection. We have already attempted to settle with what 

 order of the properties of this part the atmosphere in this case 

 holds its relation, and we have found it to be with the pro- 

 perties of life. 



13. Thus it appears necessary that the properties of the seat 

 should have undergone a change, preparatory to that of irritation 

 by atmospherical influence, to which our symptom has been more 

 immediately attributed. This change implies a different form or 

 combination of the properties making the life of the part; the 

 atmosphere is related with this form (which, as it tends to disease, 

 may be called the disordered condition), so as to produce the 

 symptom in question; while it is not related with the healthy state 

 of these properties, so as to produce such an effect in conjunction 

 with them. 



14. This first deviation from a healthy state of the proper- 

 ties, this peculiarity in the constitution of the spirit, this state 

 which precedes the symptoms of disease, by wjiich we judge of 

 its presence, is expressed familiarly by the word predisposition. 

 This predisposition we have shewn to consist of a change of the 

 combination, or assemblage of the properties which constitute a 

 healthy state. 



15. The state of predisposition must precede every spon- 

 taneous disease, at least in its primary seat: this, without recurring 

 to particular examples, is sufficiently obvious from the fact that 

 the same exciting causes, as they are called, do not affect others in 

 the same manner, and perhaps have entered into the habits of the 

 individual who suffers the disease for many years, as in our 

 example, without being attended by preternatural effects. Our 

 next inquiry is into the history of this state of predisposition. 



1(>. Our topic is "otherwise thus expressed: Why does that 

 change take place in the properties of a seat, which disposes them 

 for disease? We infer, in agreement with our general principles, 

 that this change, like every other, is accomplished by an act of 

 causation, of which there are two modes, viz. the addition and the 

 abstraction of constituents. We have many times before led up 

 to that point where analysis ends: here again we must recur to if. 

 It requires, in order to specify what properties are added to, or 

 what taken away from, the healthy, in order to produce the pre- 

 disposed condition; for this purpose it requires that we should 

 know the properties concerned in either case; but as they are 

 not objects of the senses, we cannot pursue the analysis in thit 

 strict way. 



17. Our first change of the healthy state in a particular seat 

 is thus easily reduced to a conformity with our general principles. 

 But, iq admitting the conformity in this instance, the following 

 difficulty occurs. If the predisponent condition is produced, 

 either by properties added or causes taken away, it would appear 

 that they must, in the former., be communicated from some oilier 



N N. 



