222 PHYSIOLOGY. 



other distinction of the former than that of agreeable or dis- 

 agreeable. Subdivisions have been attempted, but with no con- 

 sent of mankind so as to be expressed with any precision in 

 common language. The sensation, therefore, is probably much 

 varied in different men, and gives room for idiosyncrasies, which 

 accordingly appear without our being able to refer them to any 

 particular classes or orders of odours ; and the effects are not 

 less remarkable by the operation of the same odour upon dif- 

 ferent persons, than by its being so powerful in its degree, pro- 

 ducing syncope, hysteria, and epilepsy. 



These peculiar effects of sensations are manifestly extended 

 to the alimentary canal. In this, and particularly in the stom- 

 ach, the sensibility is not correspondent to the general sensi- 

 bility and irritability of the whole system ; for there are in- 

 stances of strong persons moved by very small doses of emetics ; 

 whilst, on the other hand, there are seemingly weakly persons 

 who are not moved but by very large doses of the same. 



There are instances of sensibility in the stomach that are 

 peculiar to certain persons, and appearing in few others. But 

 I must acknowledge, that with regard to several of these idio- 

 syncrasies, it is not easy to determine whether their effects de- 

 pend upon an impression made upon the nerves of the stomach, 

 or upon a modification which these substances give to the fer- 

 mentations and solutions that take place there. (See page 

 53.) 



In any attempts to account for these peculiarities, it ought 

 to be kept in view, that the stomach is not only affected by sen- 

 sations depending upon impression, but likewise by those which 

 depend upon consciousness, or a perception of the state of its 

 own action ; and that undoubtedly many of its sensations are of 

 the latter kind. 



It does not seem necessary to enter upon the consideration 

 of the idiosyncrasies of the intestinal canal, as they are to be ex- 

 plained from the same degree of sensibility that may be peculiar 

 here as in the stomach. What farther may arise from a pecu- 

 liar state of the bile, or other fluids poured into the intestines, 

 we cannot pretend to judge. The various state of the alvine 

 excretion depends upon many different causes which there is no 

 place for considering here ; but it is most likely that some of 



