PREFACE. 



ALL diseases originate in the exuberance, deficiency,, 

 or retrograde action, of the faculties of the sensorium, 

 as their proximate cause; and consist in the disordered 

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

 fect of the exertions of those disordered faculties. 



The sensoriurn possesses four distinct powers, or fa- 

 culties, which are occasionally exerted, and produce all 

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

 the faculties of producing fibrous motions in conse- 

 quence of irritation, which is excited by external bo- 

 dies; in consequence of sensation, which is excited by 

 pleasure or pain; in consequence of volition, which is 

 excited by desire or aversion; and in consequence of 

 association, which is excited by other fibrous motions. 

 We are hence supplied with four natural classes of dis- 

 eases derived from their proximate causes; which we 

 shall term those of irritation, those of sensation, those 

 of volition, and those of association. 



In the subsequent classification of diseases I have 

 not adhered to the methods of any of those who have 

 preceded me; the principal of whom are the great 

 names of Sauvages and Cullen; but have nevertheless 

 availed myself, as much as I could, of their definitions 

 and distinctions. 



The essential characteristic of a disease consists in 

 its proximate cause, as is well observed by Doctor 



