x PREFACE. 



In Sea. XXXIX. 8. 4. and in Clafs II. i. i. i. we 

 have endeavoured to give names to four links of animal 

 caufation, which conveniently apply to the clafTification 

 of difeafes ; thus in common nictitation, or winking with 

 the eyes without our attention to it, the increafed irrita- 

 tion is the proximate caufe ; the ftimulus of the air on 

 the dry cornea is the remote caufe ; the clofmg of the 

 eyelid is the proximate effect ; and the diffufion of tears 

 over the eyeball is the remote effect. In fome cafes two 

 more links of caufation may be introduced ; one of 

 them may be termed the preremote caufe ; as the warmth 

 or motion of the atmofphere, which caufes greater 

 exhalation from the cornea. And the other thepoft-re- 

 mote effect;; as the renewed pellucidity of the cornea; 

 and thus fix links of caufation may be expreffed in 

 words. 



But if amid thefe remote links of animal caufation any 

 of the four powers or faculties of the fenforium be intro- 

 duced, the reafoning is not juft according to the method 

 here propofed ; for thefe powers of the fenforium are 

 always the proximate caufes of the contractions of an- 

 imal fibres ; and therefore in true language cannot be 

 termed their remote caufes. From this criterion it 

 may always be determined, whether more difeafes than 

 one are comprehended under one name ; a circumftance 

 which has much impeded the inveftigation of the caufes, 

 and cures of difeafes. 



Thus the term fever, is generally given to a collection 

 of morbid fymptoms ; which areiadeed fo many diftinct 



difeafes, 



