258 SENSATION AND THE SENSIFEROUS ORGANS. [LECT. 



the nerve fibres, passes along them with a measurable 

 velocity, and, finally reaching the sensorium, is imme- 

 diately followed by the sensation. 



Thus, modern investigation supplies a represent- 

 ative of the Epicurean simulacra in the volatile 

 particles of the musk ; but it also gives us the stamp 

 of the particles on the olfactory epithelium, without 

 any transmission of matter, as the equivalent of the 

 Aristotelian "form;" while, finally, the modes of 

 motion of the molecules of the olfactory cells, of the 

 nerve, and of the cerebral sensorium, which are 

 Hartley's vibrations, may stand very well for a double 

 of the " intentional species " of the Schoolmen. And 

 this last remark is not intended merely to suggest a 

 fanciful parallel ; for, if the cause of the sensation is, 

 as analogy suggests, to be sought in the mode of 

 motion of the object of sense, then it is quite possible 

 that the particular mode of motion of the object is re- 

 produced in the sensorium ; exactly as the diaphragm 

 of a telephone reproduces the mode of motion taken up 

 at its receiving end. In other words, the secondary 

 "intentional species" may be, as the Schoolmen thought 

 the primary one was, the last link between matter and 

 mind. 



None the less, however, does it remain true that 

 no similarity exists, nor indeed is conceivable, between 

 the cause of the sensation and the sensation. Attend 

 as closely to the sensations of muskiness, or any other 

 odour, as we will, no trace of extension, resistance, or 

 motion is discernible in them. They have no attri- 

 bute in common with those which we ascribe to 



