PAIN IN DEEP STR UCTURES. 989 



higher threshold of intensity of stimulus than does the other, does not 

 supply a final criterion for judging the question under consideration. 

 There may coexist in the skin two sets of true tactual organs, the one 

 more sensitive to touch than the other. 



Some observers who admit distinction between " pressure spots " (called 

 here "touch spots") and "pain spots," affirm the perception of a quality of 

 "contact" in skin sensation in addition to qualities of "pressure" and of 

 "pain." 1 They find "contact" quality in the sensations both from "pain 

 spots" and "pressure spots." 2 Some affirm it also and I agree with them 

 in this in the sensations evoked at temperature spots, 3 although less prominent 

 in the perception than is the quality of cold or warmth respectively. Tactile 

 and temperature stimuli are, it may be recalled, not invariably discriminable 

 when applied to some regions of the skin of the back. It is true, however, 

 that if one only out of the four sets of end-organs in the skin can evoke the 

 pain psychosis, then that one can quite appropriately be considered a specific 

 " pain organ." Nor in the skin especially is there any teleological difficulty in 

 the acquirement by the body of a specific set of nerve fibres and nerve organs 

 for sensations of pain. Thus it is found that certain forms of common sensa- 

 tion (e.g. sexual voluptas, tickling), peculiarly potential of pleasurable emotion, 

 have been evolved in special connection with certain fields of skin which are 

 not pre-eminently sentient for ordinary "touch." 



Let it be granted that the above evidence still leaves it open to 

 regard the skin as possessing, apart from tactual and thermal sense, a 

 specific dolorific sense as well. What have the other sensifacient regions 

 of the body, which can as unequivocally as the skin initiate physical 

 pain, to offer in comment upon such a view ? There are " deep " pains 

 as certainly as there are cutaneous or " superficial." Deep structures 

 occasioning pain are the organs of bodily movement and the viscera. 

 Are these structures also endowed with specific nerve fibres for a pain- 

 sense. The afferent nerves of the organs of bodily movement are the 

 ministers of the so-called muscular sense. (For detailed account of 

 them and their function, reference must be made to the article on 

 " Muscular Sense "). They are, as regards their distribution to tissue, and 

 probably also the details of their function, divisible into several sub- 

 groups. The pain, which under unusual circumstances is evoked from 

 the parts supplied by this sense, may either express the excessive 

 reaction of specific " muscular sense " nerves, or the reaction of separate 

 pain fibres, admixed with the fibres proper to " muscular sense," just as 

 it was granted, for the argument above, " pain fibres " exist admixed 

 among the other afferent cutaneous nerve fibres. 



The stimuli which provoke pain from the deep structures, such as 

 muscles and joints, appear to be mechanical in quality ; in fact, the same 

 in kind as those which normally must furnish the impressions at basis 

 of the muscular sense. Haller's 4 original experiments vouch for the 

 inadequacy of an exhaustive number of chemical and thermal stimuli. 

 More than that, his experiments, together with other observations, show 

 that certain mechanical insults to muscle and tendon are quite impotent 

 to excite pain. 



In reading those earlier experiments, one is struck by two circumstances 



1 Kiesow,Zischr.f.Psychol. u.PhysioLd.Sinnesorg., Hamburg u. Leipzig, 1896, Bd. x.S.139. 



2 Dessoir, 1892, Nagel, 1895, Kiesow, 1896, and, if I understand him correctly, Gold- 

 scheider ("Ueber den Schmerz," Berlin, 1894) throughout his analysis of skin senses, 

 1885-1895. 



3 Kiesow, loc. cit. 4 " De Partibus," Gottingen, 1752. 



