438 ELEMENTARY PHYSIOLOGY less. 



of musk diffuse themselves with great rapidity through 

 the nasal passages and give rise to the sensation of a 

 powerful odour. But beyond a broad notion that the 

 odour is in the nose, this sensation is unaccompanied 

 by any ideas of locality and direction. Still less does 

 it give rise to any concejjtion of form, or size, or force, 

 or of succession, or contemporaneity. If a man had 

 no other sense than that of smell, and musk were the 

 only odorous body, he could have no sense of outness — 

 no power of distinguishing between the external world and 

 himself. 



Contrast this with what may seem to be the equally 

 simple sensation obtained by drawing the finger along the 

 table, the eyes being shut. This act gives one the 

 sensation of a flat, hard surface outside one's self, which 

 sensation appears to be just as simple as the odour of 

 musk, but is really a complex state of feeling compounded 

 of— 



(a) Pure sensations of contact. 



(6) Pure muscular sensations of two kinds, — tie one 

 arising from the resistance of the table, the other from the 

 actions of those muscles which draw the finger along. 



(c) Ideas of the order in which these pure sensations 

 succeed one another. 



(d) Comparisons of these sensations and their order, 

 with the recollection of like sensations similarly arranged, 

 which have been obtained on previous occasions. 



(e) Recollections of the impressions of extension, flat- 

 ness, &c., made on the organ of vision when these previous 

 tactile and muscular sensations were obtained. 



Thus, in this case, the only pure sensations are those 

 of contact and muscular action. The greater part of what 

 we call the sensation is a complex mass of pi'esent and 

 recollected sensations and judgments. 



Should any doubt remain that we do thus mix up our 

 sensations with our judgments into one indistinguishable 

 whole, shut the eyes as before, and, instead of touching 



