THE SKIN AND COMMON SENSATION. 9 Si 



long root fibres of the dorsal spinal column, without decussation right up 

 to the dorsal column nuclei. Muscular sensation is not affected by the 

 diseases that implicate the above-described spinal path, at least, muscular 

 co-ordination is not obviously disturbed by them. The severest muscular 

 cramps and fatigue do not induce associated skin sensations. 



Some individuals never have a presentation of a certain sense without the 

 occurrence of a presentation of another sense, hence " coloured audition," 

 photosms," etc. These are called "secondary sensations," the word sensa- 

 tion being employed in its broad sense to cover presentational perceptions. 1 

 A somewhat similar phenomenon, also familiar to many, is the "referred" or 

 "associate" sensation, Mitempfindung. In it excitement of one sensifacient 

 organ or part produces, besides its own proper sensation, a sensation referred to 

 another part. As not the " reference " but the " association " is the peculiarity, 

 the reference being only the ordinary process, which in this case by its 

 operation calls attention to the association, the term "referred" is not 

 altogether happily applied to the phenomenon. "Sympathetic," the term 

 used at the beginning of this century, 2 seems better, and is especially 

 appropriate because of the proneness of associate sensations to be of the nature 

 of pain. An often cited associate sensation is the tickling in the nose which is 

 felt on looking at a brilliant light; 3 here probably the association is less 

 between the optic nerve and the nasal branches of the trigeminus than 

 between the branches of the trigeminus supplying the eyeball and those 

 supplying the nose. Pain in the shoulder associated with liver disease was 

 similarly regarded, and a fanciful speculation offered in explanation for it by the 

 anthropotomist. What Americans call "the ice-cream nerve" pain on the 

 forehead on eating a cold substance is a better example. By applying a 

 " mustard leaf " over the front of the upper part of the sternum, I can produce, 

 in myself, the sensation of a patch of hot, unpleasantly tingling character, 

 referred to the inner side of each upper arm, just above the inner condyle ; 

 each patch seems oval, the long axis directed up the arm, and extending for 

 about 3 in. During the phenomenon I cannot really rid myself of the belief 

 that the skin there must be looking red, but no flush is found. In this case 

 the associated sensations and the stimulus applied lie, as shown by delimitations 

 of the cutaneous segmental-nerve areas, 4 both of them within the same 

 segmental area. 



In connection with viscera, the phenomenon takes forms that might 

 almost be spoken of as " illusions of pain." The associate pains 

 " sympathies " literally of visceral disease have been recorded, and 

 dwelt on by M. Traube, 5 Quincke, Hilton, 6 Brown-Sequard, 7 Dana, 8 Head, 

 J. Mackenzie, 9 and others, but it is especially since the work of Head 10 

 that the previously isolated facts have been systematically extended 

 and ably correlated, so as to assume scientific importance. Pains are 

 initiated by the afferent nerves of viscera in certain skin areas. The 

 importance of this for the present argument lies in the fact that the 

 central pain-path seems shown by this evidence to be to some extent a 



1 " Secondary sensation " has been used by Gad and Goldscheider in another and prefer- 

 able sense. See Arch.f. PhysioL, Leipzig, 1892, and this article, p. 998. 



2 Johann Miiller, Purkinje, etc. 



:i Muller's "Elements of Physiology," 1832-1837, vol. i. 



4 Sherrington, Phil. Trans., London, 1892. 



5 See Bruns, Ztschr. f. Psychol. u. PhysioL d. Sinnesorg., Hamburg and Leipzig, 1896, 

 Bd. ix. S. 134. 



6 "Rest and Pain," London, 1855. 



7 "Researches on Epilepsy," Boston, 1857. 



8 New York Med. Journ., July 1887. 9 Brain, London, 1894, vol. xvi. 



10 Brain, London, 1893, vol. xvi. pp. 1-133 ; 1894, vol. xvii. pp. 339-480 ; 1896, vol. 

 xix. pp. 153-276. 



