9 8 4 



CUTANEOUS SENSATIONS. 



those for warmth, with pain. On the other hand, the nerves for pure 

 touch, and perhaps those of the muscular sense, must be fairly separate 

 centrally from those of pain. 



It has been pointed out l that the sensations of the intellectual senses 

 have a power of cohesion, of integrating; whereas "hunger, thirst, 

 nausea, and visceral feelings in general cohere little with one another 

 and with other feelings, and thus integrate but feebly." They interfere 

 and are incompatible with and even displace other sensations. Cutaneous 

 " pain " soon and easily overpowers, cancels, and obscures other specific 

 qualities of sensations arising simultaneously. We know from experi- 

 ence that from certain stimuli certain specific sensations must under 

 ordinary circumstances arise, yet when pain is added to these they are 

 inhibited, not felt. This argues for the suppression of one reaction by 

 intervention of a second of a different kind, rather than for any alteration 

 of mere intensity in the earlier. It is as if with a certain violence of 

 stimulus a new sensation ousted a co-existent from all role in conscious- 

 ness. 



The central neural mechanism for cutaneous pain is certainly there- 

 fore largely distinct from that of touch, and to a certain extent from 

 cold and warmth sensations. There is evidence also that its peripheral 

 mechanism is to a certain extent distinct. The existence of separate 

 afferent nerve fibres with specific dolorific end-organs would completely 

 accord with the third hypothesis mentioned above at the outset. The 

 chief arguments in its support can briefly be cited as follows. 



There are some regions of the skin that are analgesic, though they 

 possess good tactual sense (e.g. the buccal mucosa opposite the second 

 lower molar (Kiesow)). 2 Other regions exist which are by a number of 

 observers judged to be anaesthetic as regards pure " touch," although 

 acutely sensitive for pain (cornea) (see p. 987). Analysis of the 

 functions of the skin as a sensifacient surface distinguishes within it 

 elemental points, not only for " touch," " cold," and " warmth " sensa- 

 tions, but also others, there is evidence, for " pain." Goldscheider early 

 declared that the " cold spots " and " warmth spots " can by no amount 

 of excitation be proved to initiate pain. On touching one of the latter 

 with a heated cone, a "feeling with high degree of heat quality but 

 without painful quality " 3 is produced ; although at other places than 

 " temperature spots," contact with the cone-point can be extremely 

 painful. The peculiar "burning" character of the pain produced by 

 contact of the skin with a hot object, is explained as due to the 

 admixture of sensations arising from the stimulated " warmth spots," 

 with pain arising from the stimulated " pain spots." It is stated 4 that 

 " touch spots " are similarly analgesic, although it is not yet altogether 

 clear that touch of a painful quality cannot be excited from them by 

 intense stimulation. It is to be remembered that the " spots " from 

 which, according to both observers, pure pain can be so easily excited 

 are extremely numerous, and it is difficult so to apply with minute 

 areal limitation an intense mechanical stimulus that it shall not affect 

 " pain spots " in the vicinity of the touch spots. 



When a small region, e.g. 1 sq. cm. of skin, in which the hairlets 



1 H. Spencer, 'Principles of Psychology, " vol. i. p. 187. 



2 Kiesow, Phil. Stud., Leipzig, Bd. ix. S. 540 ; ibid., Bd. xiv. S. 567 ; v. Frey, Ber. 

 d. Jc. sacks. Gesdlsch., Leipzig, July 1894. 



3 Op. cit. 4 Goldscheider, v. Frey, op. cit. 



