CUTANEOUS SENSATIONS 553 



it is possible to appreciate in the area under investigation the sensation 

 of pain, and to recognise roughness of an object rubbed on the skin. 

 Localisation is still somewhat diffuse and inaccurate, so that the 

 sensation evoked by a stimulus of the protopathic area may be referred 

 to some adjoining normal part of the skin. The temperature sense is 

 also present, but of a low grade. Thus heat over 38 C. and cold 

 under 24 C. can be appreciated as such, but the intervening tempera- 

 tures produce no sensation. Sensations evoked in the protopathic area 

 are strongly endowed with what may be termed ' affective ' character. 

 Thus painful stimulation is much more unpleasant when applied to 

 this area than would a similar stimulation be when applied to a 

 normal area of skin. 



In contradistinction to the deep sensibility which is diffuse, 

 protopathic sensibility is distributed in spots, so that heat and cold 

 spots, for instance, may be distinguished as on the normal skin. It is 

 interesting that the glans penis is normally provided only with proto- 

 pathic sensibility. 



EPICRITIC SENSIBILITY does not return to the desensitised area 

 until one to two years have elapsed since the division of the nerves. 

 With its return the affective character of the protopathic sensations 

 at once disappears and is replaced by an accurate discrimination of the 

 nature and extent of the stimulus ; the tactile sense proper, i.e. the 

 appreciation of the lightest touch applied to the skin and its accurate 

 localisation, belonging entirely to the epicritic sensations. The power 

 of discriminating the distance between two points applied to the skin 

 simultaneously is also a function of the epicritic sensibility. 



With the discriminating tactile sense returns also the power of 

 appreciating fine differences of temperature, i.e. differences between 

 26 and 37 C. 



This classification may be summed as follows : 



,., -IT f Pressure sense 



Deep sensibility . . including (p^^ pain 



f Skin pain 



Protopathic sensibility . -I Heat over 38 C. 



(strongly affective) I Cold under 24 C. 



Epicritic sensibility 



Tactile sense proper 

 Pain localisation 

 Discrimination 



(accurately localised) Heat and cold between 



( 26 and 37 C. 



Head and Thompson have shown that on entering the cord these 

 various sensations undergo a new grouping. Thus the pain impulses, 

 which arise in and are carried by the muscular nerves, the nerves of 



