REFERRED PAIN. 689 



comparatively little localisation of sensation in the viscera, and it is 

 doubtful whether there is any proper sense of touch. 



Referred pain. — At times diseases of the viscera give rise to 

 pain in certain parts of the skin. This is spoken of as referred pain. 

 Approximate explanation of its occurrence was put forward by Boss. 1 

 On his view, the irritation of the visceral fibres of an organ is conducted 

 to the grey matter of the cord, and there diffuses to the roots of the 

 corresponding somatic nerves, and thus causes an associated pain in the 

 area of distribution of these nerves. We may adopt the essential part 

 of this view, namely, that when the afferent autonomic fibres of a nerve 

 are affected, the primary referred pain will be in the area of the cutaneous 

 fibres of the nerve. 



It was shown by Mackenzie 2 and by Head 3 that visceral disease also 

 causes areas of the skin to be more sensitive to slight stimuli, i.e. it may 

 give rise to referred tenderness as well as to referred pain. 



On this basis it is clear that referred pain will occur in the skin 

 areas of those roots which have white rami, of those from which the 

 pelvic nerve arises, and of those nerves, if any, with which the vagus 

 afferent fibres are intimately connected. And there should not be 

 primary referred pain in any others kin areas. Indeed, Ross — influenced 

 by Gaskell's work on the visceral system — brought forward some facts 

 to show that this was the case. 



The question was followed up by Head, who has shown that, 

 whilst primary referred pain and tenderness occur in large parts of 

 the body, they do not occur in all. They do not occur in certain parts 

 of the limbs, and we have seen that some of the nerves for the limbs send 

 no fibres either to the cranial, sympathetic, or sacral autonomic system. 



From what we have said earlier, with regard to the white rami and the 

 pelvic nerve in man, we should expect the lumbo-sacral nerves, in the areas of 

 which no primary referred pain occurs, to be ordinarily the third lumbar to 

 the first sacral inclusive, sometimes also the second sacral, and possibly at 

 other times the second lumbar. According to Head, the nerves are the second, 

 third, and fourth lumbar. If this is so, either the afferent impulses pass 

 by the grey rami, or the afferent sympathetic fibres of a nerve may cause 

 primary referred pain outside the somatic area of the nerve to which they 

 belong. Referred pain by way of the vagus occurs in part of the region of 

 the fifth cranial nerve and of the upper cervical nerves ; i hence, we must 

 suppose that the roots of the vagus have intimate connection with the roots of 

 the fifth and of the upper cervical nerves. Certain deep structures of the 

 head, such as the iris, tooth pulp, tongue, cause referred pain in the skin 

 region of the fifth nerve, and, taken together, in the whole region of the fifth. 



Affections of certain of the thoracic abdominal organs frequently 

 cause referred pain both in the body and in the head or neck, i.e. both 

 above and below the brachial gap. This is naturally explained by the 

 supposition that the organs receive fibres both from the sympathetic 

 and from the vagus. 



1 Brain, London, 1888, vol. x. p. 351. 



"Med. Chrmi., Manchester, August 1892; el', also Joum. Path, and Bacteriol., 

 Edin. and London, 1893, vol. i. p. 332. 



* Brain, London, 1893, vol. xvi. p. 1 ; 1894, vol. xvii. p. 339. Cf. further on tin's 

 subject the article by Sherrington on " Cutaneous Sensibility " in this volume. 



4 Head, op. cit., 1894. 



vol. ii. — 44 



