PAIN 



367 



FIG. 219 



indescribable true sensation, the other a complex feeling allied to the 

 other general "sensations" (see below). The confusion is increased by 

 the fact that oftentimes both the sensation of pain and the unpleasant 

 feelings may be experienced at the same time, somewhat as a man may 

 feel fatigued and suffer from a toothache simultaneously. But if we 

 leave these numerous compound experiences out of our account we find 

 pain as the mental aspect of the functioning of certain sense-organs, 

 while unpleasantness is a psychological subject with which we have 

 just here no concern. Their only apparent common factor is that the 

 animal experiencing them wishes both gone and changed to their oppo- 

 sites, pleasure and pleasantness respectively. We assume, it may be 

 too dogmatically, that a little 

 positive evidence as to pain-ap- 

 paratus is worth volumes of nega- 

 tive theories in opposition to it. 

 (See also Chapter XII, under 

 Feeling, page 409). 



The Sensory Apparatus of Pain 

 was tentatively described about 

 the same time as was that of 

 touch and of the temperature- 

 senses, Goldscheider's name and 

 that of von Frey being especially 

 associated with its discovery. The 

 peripheral nerve-endings or the 

 end-organs, whatever their form, 

 are situated apparently in "spots," 

 as are those of the other senses 

 named. These spots are scat- 

 tered more evenly than in the 

 other cases over the body's sur- 

 face, and perhaps to a slight ex- 

 tent within the viscera of the body, 

 especially in the testis, ovary, kid- 

 ney, and rectum. When stimu- 

 lated mechanically or electrically 

 by points delicate enough, these 

 spots give rise to a smart, tingling pain whose one only quality is 

 that of pure painfulness, there being nothing connected with it like 

 any other sensation whatever. (On the other hand the touch-spots, 

 heat-spots, and cold-spots lack this pain-character when stimulated.) 

 From the pain-spots pressure-stimuli as small as that of 150 grams 

 per square millimeter elicit this wholly characteristic pain-sensation. 

 Several circumstances besides that of their even distribution serve to 

 distinguish them from the other cutaneous spots. Of these circum- 

 stances, their very long latent-period is perhaps the most conclusive, 

 for it is most easily measurable in exact terms. Only less so than this, 



Afferent nerve-endings in the human cornea, 

 according to Klein, oblique section: a, nerve- 

 fiber (axis-cylinder); 6, fibrils; c, terminal net- 

 work among the epithelial cells, d. Perhaps 

 these are the endings that represent pain. 



