PREFACE. 



r~T -—,-.-.■ _.- 



ALL difeafes originate in the exuberance, deficiency, 

 or retrograde action, of the faculties of the fenforium, 

 as their proximate caufe ; and confift in the difordered 

 motions of the fibres of the body, as the proximate ef- 

 fect of the exertions of thofe difordered faculties. 



The fenforium porTefies four diftincl: powers, or facul- 

 ties, which are occafionally exerted, and produce all the 

 motions of the fibrous parts of the body ; thefe are the 

 faculties of producing fibrous motions in confequence of 

 irritation, which is excited by external bodies ; in con- 

 fequence of fenfation, which is excited by pleafure or 

 pain ; in confequence of volition, which is excited by de- 

 fire or averfion ; and in confequence of affociation, 

 which is excited by other fibrous motions. We are 

 hence fupplied with four natural claries of difeafes de- 

 rived from their proximate caufes ; which we fhall term 

 thofe of irritation, thofe of fenfation, thofe of volition, 

 and thofe of aflbciation. 



In 



