THE SKIN AND COMMON SENSATION. 987 



per cent, solution, it can locally completely paralyse all endings, including 

 "painful." Chloroform, 1 locally applied with a sponge, after a temporary 

 burning sensation, leaves all forms of sensibility locally lowered. It acts on 

 different sensations in the same order of degree as cocain, but especially 

 suppresses heat-pain. Menthol, 2 after causing a temporary hypersesthesia of 

 cold spots, depresses sensibility of all forms. Orthoform, 3 in subcutaneous 

 injection, after preliminary local pain, causes local analgesia. Guaiacol acts less 

 quickly, but otherwise similarly and more lastingly, than cocain. 4 



4. The faradisation of pain spots, at any frequency above twenty 

 shocks per second, evokes a continuous sensation ; faradisation of touch 

 spots, at rates of 130 shocks per second, evokes a discontinuous vibratory 

 sensation. A similar difference between the length of duration of the 

 reaction is also traceable by single shocks or mechanical stimuli ; the 

 pain sensation fades more gradually away. 5 



5. Not only minute, but also regional, distribution is different in the 

 case of the two sets of " spots." The cornea and ocular conjunctiva are 

 rich in pain spots, but have no touch spots ; so also the glans penis. 6 

 The eyelid sweeps over the cornea without being felt. On the other 

 hand, a patch of mucous membrane inside the cheek is without pain 

 spots, 7 although provided with touch spots ; indeed, the whole of the 

 inside of the mouth is poorly provided with pain spots, although much 

 of it is extremely rich in touch spots. There is a patch of the mucosa 

 of the cheek at which faradic currents, sufficient to violently tetanise 

 the facial muscles and radiate over all the region of the upper jaw, cause 

 no trace of unpleasant sensation at the point of application. 



In examining the buccal mucosa for pain by electric stimuli, it must be re- 

 membered that there moisture renders stigmatic application difficult, and with 

 increase of area the density of the current falls. Comparison of dolorific effect 

 obtained by stigmatic stimuli elsewhere with this buccal stimulation is therefore 

 complex ; the buccal stimuli would be effectually less intense in application. 



6. The sensation from a touch spot is referred to the surface of the 

 skin ; that from a pain spot seems to radiate into the depth as well as 

 over the skin surface, and is less clearly qualified with " local sign." 8 



7. The "latent period" of skin pain is greatly longer than that of touch. 



From clinical pathology there is testimony corroborative of the physio- 

 logical. A difficulty, however, arises with the pathological evidence. The 

 pain stimulus being of intenser nature, allows the inference that the selective 

 action of disease on the fibres of a peripheral nerve may consist in limiting 

 the range of their response to the stimulus, without causing it to lose its 

 functions altogether. The plausibility of this suggests itself most in the cases 

 where there is analgesia without total anaesthesia of a part. Pressure on the 

 ulnar nerve trunk will cause partial or total anaesthesia for pain and temperature, 



1 Goldscheider, op. cit. 



2 Goldscheider, op. cit.; Sherrington, " Intemied. d. biol.," Paris, 1897, tome i. p. 84. 



3 H. de Varigny, ibid., 1897, tome i. p. 125. Orthoform is an ether from amido- 

 oxybenzoic acid. 



4 Loiselle, ibid., 1897, tome i. p. 157. 



5 Nagel, op. cit. ; v. Frey, op. cit. But cf. Bloch, Trav. du lab. de Marey, Liege, 1897, tome iii. 



6 There is a difference of opinion as to whether any touch can be felt on the cornea 

 without pain. Nagel has pointed out that touches can be felt on the conjunctiva and 

 cornea without any painful or disagreeable quality in them. It is the ease with which the 

 corneal endings provoke pain which is denoted by the term "pain spots" as used in the 

 above paragraph. See also Hotter, "Diss.," Erlangen, 1878; M, Dessoir, Arch. f. Physiol., 

 Leipzig, 1892. S. 175. 



' Kiesow, Phil. Stud., Leipzig, 1894, Bd. ix. S. 510 ; v. Frey, loc. cit. 

 8 E. H. Weber, op. cit. 



