706 FUNCTIONS OF THE SPINAL CORD fCH. XL1X. 



sensations are subserved by nerve-fibres which are distributed with 

 the muscular nerves. It is by means of the sensory nerves of muscles, 

 tendons, and joints that we are aware of the position of our limbs, 

 and the extent of muscular contraction. 



After a time true cutaneous sensation returned when the severed 

 nerve regenerated, but it was not until many months elapsed that 

 sensation was as sharp and as accurately localised as it was before 

 the nerve had been cut. The first sensations that returned enabled 

 Head to feel pain, to distinguish large differences of temperature, 

 and to localise the position of a touch somewhat inaccurately. Head 

 terms such imperfect sensations protopathic. The ability to localise 

 accurately, to distinguish small differences of temperature and the 

 finer distinctions generally of cutaneous sensations, returned later, 

 and are spoken of as epicritic. We may thus divide the main sensa- 

 tions coming from the periphery of the body into deep and 

 cutaneous ; and the cutaneous sensations into protopathic and epi- 

 critic. The other classification into sensations of touch, heat, cold, 

 and pain, cuts across the first; thus we may have pain that is of 

 deep or of cutaneous origin ; we may have temperature sensations 

 which are both rough or protopathic, and accurate or epicritic ; and 

 we may feel pressure and localise it by means of the cutaneous sense 

 proper, or by the stimulation of the sensory nerves in the deeper 

 structures. Whether different nerve-fibres are concerned in the 

 transmission of protopathic and epicritic impulses is a matter of 

 doubt. It is quite possible that the same fibres may be concerned 

 in the transmission of both. 



Diseases of the spinal cord in man usually are widespread and 

 affect many tracts ; the disorders of muscular paralysis and of sensa- 

 tion thus produced will therefore be complex. The more limited the 

 lesion, the fewer tracts will be affected, and such conditions are 

 therefore more on all fours with these localised lesions or sections 

 of tracts which can be performed on animals. The operation of 

 hemisection in an animal produces paralysis of the same side of the 

 body below the injury. So it is in a man in whom disease has pro- 

 duced an interruption of the pathways on one side only of the cord. 

 But such an animal or man (and the observation is more accurate in 

 man) will not have lost all sensation on the same side ; tactile 

 discrimination, and the motorial sense will have largely disappeared, 

 but sensations of pain, of heat, and of cold will still remain, because 

 the tracts which convey such impulses cross over in the cord at 

 varying levels after entering it, and therefore any loss in such sensa- 

 tions will occur on the opposite side to that which is injured. 



It was no doubt absence of correct knowledge on this question 

 that led Schiff to imagine that impulses translated by the brain, as 

 sensations of temperature and pain, travelled up by the grey matter, 



