284 



CHAP. IV. 



Disease of the assimilating, of the regular dependent, and of the 

 occasional Properties of Life* 



1. THERE are but few (perhaps not any) examples of 

 disease which is confined wholly to one part. There are many 

 instances of disease of one part, in which the organic system else- 

 where does not perceptibly suffer: but these are attended with 

 pain or disordered motion, which is sufficient to prove an exten- 

 sion of the diseased state. In the organic system however a per- 

 son may have an ulcer in the leg, or a tumour upon the shoulder, 

 or an herpetic disease upon some spot of the skin, or a stricture of 

 the urethra, &c. without any sensible derangement of the same 

 system elsewhere. But even in these instances we cannot prove 

 that the change is entirely local, unless it may be shewn, 1st, that 

 the natural condition of the seat is not a dependent one, by which 

 disorder might originate in another sphere; and, 2nd, supposing 

 the disease to originate in its apparent seat, that no other is so 

 connected with it as to participate in its modifications. But if it 

 is possible that any part should possess only an assimilating life, 

 that no other part is dependent upon it, and that the condition of 

 disease does not open any new or preternatural relation, then it is 

 possible that the assimilating life of such part may become exclu- 

 sively diseased by that progressive causation which has been 

 described. 



2. It happens however in most instances of disease, that this^ 

 state prevails in more than one seat. In such instances these two 

 alternatives are to be discriminated: 1st, whether the diseases 

 occupying different seats are not independent of each other? 2nd, 

 whether the primary produces the secondary disease? 



3. If in the course of a fever an abscess should form in one 

 axilla, and a week afterwards an abscess should form in one groin; 

 if the eruption of the small-pox should appear first in the face and 

 then be extended over the whole body; if a tubercle should form in 

 the liver, and a month afterwards a vomica should burst in the 

 lungs; if a venereal ulcer should form in the throat, and six weeks 



