48 PHYSIOLOGY CHAP. 



by Schittenhelm and Spearman, in cases of lesions of the spinal 

 cord, the power of localising sensations in the affected limbs was 

 almost normal, but the patient was unable to discriminate the 

 points of the compass applied to the thigh. 



IX. Those sensations are termed -painful which are character- 

 ised by an affective tone of physical or corporal discomfort, even 

 when this is low in intensity. Certain olfactory and gustatory 

 stimuli can produce disagreeable sensations even at their affective 

 threshold ; certain too vivid contrasts of colours, too harsh 

 dissonances of musical tones, offend eye or ear. No one, how- 

 ever, speaking accurately, will apply the term painful to these 

 sensations, in the sense that this term is applied to the discomfort 

 produced by a wound or burn. Pain is a sensation sui generis 

 which cannot be confused with the affective tone that sometimes 

 accompanies the so-called specific sensations. Further, the 

 sensation of pain is one of the simplest psychical states, and 

 cannot be transformed into perception. We may feel pain 

 without perceiving its cause and projecting it into the external 

 world. When, on the contrary, we smell a bad odour, or taste a 

 nauseating food, our disagreeable sensations are associated with 

 the perceptions of something external to ourselves, which acts 

 on our smell or taste. The same holds good for unpleasant 

 auditory and visual sensations. 



So, too, the specific cutaneous sensations (of contact, cold, or 

 heat) are quite distinct from sensations of pain. It is true that 

 on exciting any point of the skin by stimuli of excessive strength 

 or duration we can easily provoke painful sensations, which with 

 increased strength of stimulus may produce reflex cramps, mental 

 disturbances, fainting, etc. But it would be a mistake to interpret 

 this fact by assuming that there is a painful component inherent 

 in sensations of pressure, warmth, or cold which increases dis- 

 proportionately when the stimulus and the reaction to it become 

 violent. In a moderate tactile or thermal sensation there is no 

 trace of pain. A painful sensation aroused by too powerful 

 compression of the skin never appears to any one on introspective 

 examination as an excessive tactile sensation, although the 

 stimulus is only a stronger application of the contact. The 

 pain caused by a burn is not felt as a sensation of excessive heat. 

 Both violent compression and excessive heat when applied to the 

 skin produce intense pain that dominates the specific sensations 

 of pressure or heat, and suppresses them altogether. 



This brings us to the question whether the nerves and the 

 specific end-organs for pressure, heat, and cold are also capable of 

 giving rise to sensations of pain when excited by excessive 

 stimulation (as assumed by Hagen, Lotze, Wundt, Kichet, and 

 others), or whether the skin contains specific nerve-endings and 

 the central nervous system distinct centres for pain sensations, 



