PREFACE. ix 



fore does not belong to the clafs of Senfation. As the 

 pain is caufed by increafed or decreafed action of the 

 membranes of the tooth, and thefe actions are owing to 

 the increafe or decreafe of irritation, the difeafe is to be 

 placed in the clafs of Irritation. 



To difcover the order it muft be inquired, whether 

 the pain be owing to increafed or defective motion of 

 the pained membrane ; which is known by ihe concom- 

 itant heat or coldnefs of the part. In tooth-ach without 

 inflammation there is generally a coldnefs attends the 

 cheek in its vicinity ; as may be perceived by the hand 

 of the patient himfelf, compared with the oppofite cheek. 

 Hence odontalgia is found to belong to the order of de- 

 creafed irritation. The genus and fpecies muft be found 

 by infpecting the fynopfis of the fecond order of the clafs 

 of Irritation. See Clafs I. 2. 4. 12. 



This may be further elucidated by confldering the 

 natural operation of parturition ; the pain is occaiioned 

 by the increafed action or diftention of the veffels of the 

 uterus, in confequence of the ftimulus of the fetus ; and 

 is therefore caufed by increafed irritation ; but the ac- 

 tions of the abdominal mufcles in its exclufion are cauf- 

 ed by the pain, and belong to the clafs of increafed fen- 

 fation. See Clafs II. i. i. 12. Hence the difficulty of 

 determining, under what clafs of difeafes parturition 

 mould be arranged, confifts in there being two kinds of 

 difeafed actions comprehended under one word ; which 

 have each their different proximate caufe, 



VOL. II. b In 



