SENSATION AND THE SENSIFEROUS ORGANS. 267 



the nerve fibre ; while this last change is also only a 

 mediate cause of sensation, depending, as it does, upon 

 the change which it excites in the sensorium. 



The sense organ, the nerve, and the sensorium, taken 

 together, constitute the sensiferous apparatus. They 

 make up the thickness of the wall between the mind, 

 as represented by the sensation "muskiness," and the 

 object, as represented by the particle of musk in contact 

 with the olfactory epithelium. 



It will be observed that the sensiferous wall and the 

 external world are of the same nature; whatever it is 

 that constitutes them both is expressible in terms of 

 matter and motion. "Whatever changes take place in the 

 sensiferous apparatus are continuous with, and similar to, 

 those which take place in the external world.* But, 



* The following diagrammatic scheme may help to elucidate the theory 



of sensation : 



Mediate Knowledge 



< ' -v Immediate 



Sensiferous Apparatus Knowledge 



Physical World 



Mental World 



Not Self 



Self 



Non-Ego or Object 



Ego or Subject 



Immediate knowledge is confined to states of consciousness, or, in other 

 words, to the phenomena of mind. Knowledge of the physical world, or 

 of one's own body and of objects external to it, is a system of beliefs or 



