CHAPTER XV. 



Sense of touch Difference between touch and feeling. Tactile sensibility 

 and general sensibility 1 ' Organ of touch. Sensation of contact ; dif- 

 ference in the sensibility of different regions of the body ; simple contact, 

 shock, vibration. Sensation of pressure; relative aptitude of different 

 regions in appreciating it ; variable sensation according to the form of 

 the body and the extent of its surface. Sensation of temperature, variable 

 according to the temperature of the skin, the density of bodies, and the 

 surface in contact : identical sensation from contact with a body very hot 

 and very cold; relative sensibility of different regions to temperature. 

 The touch; its delicacy. The touch compared with the other senses; 

 illusions of touch; persistence of tactile impressions, sensations from in- 

 ternal or subjective causes; causes which modify feeling. 



Touch and feeling. Tactile sensations, like all others, are 

 more or less complete according as the attention is, or is not, 

 directed to them. The contact of a foreign body with any 

 sensitive portion of the organism is revealed to us \)j feeling, 

 and it is by touch that we discover the form, resistance, and 

 temperature of this body. Feeling may be involuntary, touch 

 is an act of the will; there is therefore the same difference 

 between feeling and touch that there is between seeing and 

 looking; between hearing and listening, scenting an odour and 

 smelling it, perceiving a flavour and tasting it. 



We must also distinguish between impressions due to 

 general sensibility and tactile sensations proper; thus, if we 

 knock the elbow we feel an acute pain along the course of 

 the ulnar nerve, but the impression produced on the skin is 

 perfectly distinct from this deeper suffering when not entirely 

 masked by it. It is the same in sensations resulting from a 

 shock to the right hypochonder which produces a pain in the 

 liver. All the tissues which receive nerves of sensation may 



