99 6 CUTANEOUS SENSATIONS. 



physical stimuli, by want of differentiation rather than height of differentiation 

 of end-organ as the more probable. 



On the other hand, instead of supposing that the hypothetical 

 specific pain nerves are each and all normally and delicately amenable 

 to a range of variety of stimuli, for whose appreciation elsewhere a 

 whole series of sense organs is required, it may be answered that there 

 is no objection to supposing that the skin has two or three different 

 species of specific pain nerves. For this belief there appears at present 

 no decisive evidence, but there is the analogy with muscular and visceral 

 nerves. 



On the hypothesis of the existence of a specific pain-sense it would 

 be expected that excitation of the cerebral cortex would give rise to 

 some evidence of production of pain. The cerebral cortex, which 

 contains, as is known, fields for the termination of so to say each avenue 

 of sense, should on that view excite pain sensations. This does not 

 appear in fact to be the case. The well-known experiments of Haller, 

 Bichat, Budge, etc., besides bedside evidence, and the opportunities 

 of electrical excitation, do not bear out the expectation. Epilepsy, so far 

 as I can learn, hardly ever includes in its prodromata a " pain " aura, 1 

 although other orders of sensation — visual, auditory, tactual, thermal, 

 gustatory, and odorous — seem each laid under contribution. 



On the other hand, the dogs from which Goltz had removed the cerebral 

 hemispheres reacted to "painful" stimuli in a way which was interpreted as 

 evidence of the persistence of physical pain. Such evidence is, however, after all, 

 equivocal for the point, as is the reflex vocalisation noted in the rat — and I have 

 heard it in the monkey — elicitable even in the first hour after cerebral ablation, 

 anterior to the corpora quadrigemina. We reflect that in this condition the 

 contrast of the sensible world as "me" and "the rest" seems from other 

 evidence gone, and the animal has become "impersonal." In all these cases 

 the working of the machinery of expression is but a dubitable sign for the 

 actual existence of the feeling which is under ordinary conditions " expressed." 



On the whole, it would appear as if the deep sensory nerves, the 

 visceral and the musculo-articular, and of the superficial sensory nerves, 

 the cutaneous, possess the power of evoking physical pain ; and it 

 appears significant for this fact that these are the sensory channels 

 which inform the sentient self of the condition of that half of its 

 sensible universe, its bodily "me belonging to self." It is impos- 

 sible to think that the normal functions of three sets of afferent 

 nerves of such different distribution and physiology as the visceral, 

 musculo-articular, and cutaneous, are all the same, although the dolorific 

 actions from them appear so similar. Bodily pain would therefore 

 seem less a single specific order of sensation than, like local sign, a 

 quality attaching in common to a certain non-universal group of specific 

 sensations. Pain has no one specific stimulus with which it can be 

 correlated. This view of course relinquishes the conception of any specific 

 pain-sense, also, strictly speaking, of " pain " nerve fibres. But I re- 

 cognise that it may be convenient to distinguish, when certain apparatus 

 especially readily ministers to pain, some nerves as " dolorific " or " pain- 

 nerves " ; as in the skin where certain nerves develop sensations with 

 pain quality dominant, almost to the exclusion of all other (as muscle 

 nerves evoke dominant local sign). This usage will at least serve as a 



1 See, as a rare instance, the case given by Pierce Clark, Am. Journ. Insan., Utica, 

 N. Y. ( July 1897. 



