PHYSIOLOGY. 221 



All this might be illustrated more fully ; but perhaps we 

 have insisted long enough upon what may by many be thought 

 perhaps too much depending upon conjectural reasonings. It 

 no doubt may, in some respects, be liable to this imputation ; 

 but I should fain hope that it may serve to lay the foundation 

 of speculations which must be pursued before we can explain 

 the important and therefore necessary doctrines concerning the 

 temperaments of men. 



OF IDIOSYNCRASIES. 



The term Idiosyncrasies has been confounded with that of 

 temperaments ; but I mean here to express by it those condi- 

 tions of certain persons whereby certain functions of the whole 

 or of particular parts of the body are affected by applications 

 made to them, very differently from what these functions are 

 affected in others, and very differently from what they are in 

 persons seemingly of the same general temperament. 



Of these idiosyncrasies, the greater part of them seems to me 

 to consist in a preternatural degree of the sensibility or irritabil- 

 ity of certain parts of the system, or in a peculiar sensibility or 

 irritability of the whole body, or in particular parts of it, with 

 regard to certain applications, and to those only* 



Of such idiosyncrasies, those that have been the most taken 

 notice of are those which occur with respect to the effects of 

 taste and odour. Tastes are of considerable variety, but they 

 are reduced to certain classes and orders, in which the most part 

 of men are so well agreed, as to show that the operation is near- 

 ly the same in all of them. This certainly happens with re- 

 spect to the simple sensation ; but with respect to the reflex of 

 agreeable or disagreeable, this is often considerably different in 

 different persons, and shows that there is room here for an idio- 

 syncrasy, which accordingly takes place ; and there are many in- 

 stances of it in the records of physic. 



The instances, however, of a peculiar aversion in particular 

 persons to certain odours, are much more frequent. The re- 

 cords of physic are full of them ; and examples of them are 

 known almost to every body. The sensations arising from 

 odour seem to be more various in different men than those aris- 

 ing from taste ; so that mankind have hardly established any 



