THE HUMAN BODY. 



experimental and pathological evidence that the paths taken in 

 the spinal cord by nerve impulses causing pain are different 

 from those leading to a consciousness of touch. If certain 

 parts of the cord are cut in the thoracic region of a rabbit, 

 gentle touches on the hind limb appear to be felt ; the animal 

 erects its ears or moves its head: but powerful stimulation of 

 the sciatic nerve causes no signs of pain, while if the posterior 

 white columns be cut the animal still can feel stimuli applied 

 to the hind limb and sufficient to cause pain under normal 

 conditions, but it appears insensible to gentle pressure on the 

 skin. In human beings very similar phenomena have been 

 observed in cases of spinal-cord disease : and in a certain stage 

 of chloroform or ether narcosis the patient feels the surgeon's 

 hand or his knife where it touches the skin, but he experiences 

 no pain when deeper parts are cut. 



Such considerations seem to lead to the conclusion that the 

 nerve-fibres and sense apparatuses concerned with painful 

 sensations are quite distinct from those of all the special senses. 

 If that be so we must also assume that there are "pain" 

 fibres very widely distributed over the skin and through most 

 other parts of the Body, and usually not so stimulated as to 

 cause sensations which are present in consciousness. In acci- 

 dent or disease the afferent impulses become powerful enough 

 to arouse perception and imperiously call attention to danger. 

 The nerve-fibres concerned may be named " fibres of common 

 sensibility," and there is reason to believe that, normally, 

 feeble afferent impulses travel along them from nearly all 

 organs to the fore brain ; but so weak and so uniform as not 

 to excite a perceived feeling: these impulses would thus form 

 a great background of subconscious feeling, on which special 

 points from time to time become conspicuous as one or other 

 nerve of special sense is stimulated or some fibre of common 

 sensibility is abnormally excited. So far as the epidermis is 

 concerned, the axis-cylinder branches, which end in it with- 

 out any special terminal apparatus, may be specially fibres of 

 common sensibility. 



Pains can be localized though but only imperfectly, and 

 the less perfectly the more severe they are. The exact place 

 of a needle prick after removal of the needle (so that there is 

 no guiding concomitant touch sensation) cannot be recognized 

 as well as pin touch on the same region of the skin, but still 

 fairly well ; while the acute pain caused by a small abscess 



