366 



THE SENSES 



nerve-fibers of its own. These impulses probably go upward in the cord 

 either by the numerous short neurones in the posterior part of the gray 

 matter (more or less as pain is supposed to go) or by the posterior median 

 and posterior lateral columns. The cerebral centers connecting with 

 these organs are not definitely known as yet, but the cutaneous sensa- 

 tions in general seem to be represented far back in the Rolandic region. 

 The whole bodily surface is more or less sensitive both to heat and cold, 

 as is to a degree also the beginning of the alimentary and respiratory 

 canals. 



FIG. 218 



The temperature-spots as Goldscheider found them in the palm of a hand: 

 A, heat-spots; B, cold-spots. 



Fig. 217 exhibits two regions, each an inch square, of the same 

 locality of two persons' hands (Hall). It shows very well the mosaic 

 arrangement of the three cutaneous senses so far considered, heat, cold, 

 and touch. Goldscheider suggests that the regions in which none of 

 these sense-spots are to be found corresponds to the blind-spot of the 

 retina regions over the trunks of small nerves, which are lacking 

 there in branches and end-organs. 



PAIN. 



In both theory and practice pain is of considerable importance. 

 Several theories, biological and psychological, might be discussed, each 

 involving elements, however, beyond our present range, and each (save 

 that here described) ignoring the physiological evidence of recent years. 

 With one of the theories, that of the evolutionists, e. g., Herbert Spencer, 

 we may say that pain is the mental accompaniment of hindered biological 

 function, just as in the long run pleasure is the accompaniment of fur- 

 thered biological function. The object of pain, then, is to warn the 

 animal of threatened organic injury or of injury already received. The 

 method by which this is as a sensation is brought about is that of other 

 sensations: end-organs, nerves, and centers. The numerous conflicting 

 theories as to pain rest on, first, the ignoring of the physiological evidence, 

 as too often is the habit of purely book-instructed theorists. Second, 

 they rest on the confusion of the sharp, biting, actual pain with the 

 numberless grades of unpleasantness and the disagreeable. One is an 



