PAIN. COMMON SENSATIONS. 585 



points at which the observed person says I feel touch or I 

 feel cold or I feel heat, be carefully marked on the skin and 

 the experiment repeated on one or more subsequent days 

 the contact points for the three sensations are found to be 

 unchanged. In certain cases of spinal -cord disease, moreover, 

 it has been noticed that tactile sensibility may be lost while 

 temperature sensibility remains; and in others that the capac- 

 ity of feeling warmth may be nearly or completely lost while 

 cold sensation remains normal. Excluding pain (' ' abnormal 

 sensation"), we must conclude that there are in the skin 

 three distinct sets of nerve-fibres : One, when excited, arouses 

 " touch " sensation; a second, " warm " sensation; the third, 

 11 cold " sensation. 



Pain and Common Sensibility. When the skin is power- 

 fully stimulated by heat, cold or pressure, or is inflamed, we 

 get a new sensation which we call pain. This is something 

 quite different from the unpleasantness caused by a dazzling 

 light or a musical discord or a disagreeable odor or taste. 

 We recognize these as being still sight or sound or smell or 

 taste sensations. Pain on the one hand is different from any 

 of the normal skin sensations and, on the other, is recog- 

 nized in consciousness as often proceeding from diseased in- 

 ternal organs from which normally we get no noticeable sen- 

 sations. An exposed healthy tendon is quite insensible to 

 touch, but if it be inflamed the slightest pressure may give 

 rise to nerve impulses causing very acute pain, and pain which 

 to the consciousness is similar to cutaneous pains or pains of 

 other organs. Since direct stimulation of the sensory nerves 

 proceeding from the skin in any way except through their 

 end organs gives rise to feelings of pain rather than to the 

 special skin sensations, and pressure and temperature feelings 

 do insensibly give way to pain feelings when the stimuli ap- 

 plied to the skin are gradually increased, it has been supposed 

 that pain is not due to excitation of a special nerve apparatus 

 of its own, but to over-excitation of the tactile apparatus. 

 On this theory it would be hard to account for the fact that 

 skin pain is so very different in modality from a touch or tem- 

 perature feeling, and to understand why it gives rise in con- 

 sciousness to conceptions concerning a condition of the Body 

 and not of some external object : it is not extrinsically referred 

 by the mind to a quality of anything but the painful part itself, 

 as a dazzling light sensation or a fetid odor is. There is also 



