SENSATION AND ITS OBJECTS. 109 



imperfect, undeserving the name of science, and 

 merely ranking on a level with other arts.* 



The sensation on the surface of the body is 

 excited by the resistance which is opposed to 

 the nerves situated under the skin, the nature 

 and the design of which depend on the pecu- 

 liarity in the arrangement of the particles of 

 the external substances ; it is from that pecu- 

 liarity that we decide whether a body be solid 

 or fluid, whether it be rough or smooth, blunt 

 or sharp. In the organs of hearing, sound in 

 general is excited by impressions on the audi- 

 tory nerves, through the medium of the tympa- 

 num ; and it is owing to the various undulations 

 of the air, modified and altered by the organi- 

 sation of the external fabric of the ear, that 

 sound in general, is made sound particular; 

 sound particular manifested by the variety of 

 tones, so distinctly perceived by those who have 

 what is called a good ear. In the organ of 

 hearing, sound may be considered the genus, 

 tones, the species. 



In the organ of smelling, the sensation of 

 odor is excited by the particles of bodies which 



* I purposely omit to notice the analysis of any part of the 

 living system, whether of animals or vegetables; because 

 chemical analysis of any portion of it, can only be accomplish- 

 ed after death ; and, consequently, during the life of the sys- 

 tem, the excretions alone are the parts, in examining which the 

 chemifct may amuse himself. 



