Release of Function in the Nervous System. 



195 



a peripheral nerve in parts of the affected area which remain sensitive to 

 pricking, but are antesthetic to light contacts ; it is also specially evident 

 during the first stage of functional recovery under identical conditions of 

 sensory dissociation. For in such circumstances impulses arising in the 

 punctate afferent mechanism can exercise their influence on the central 

 nervous system, unchecked by the more discriminative impressions ; these 

 are either absent or have not yet been fully restored. Whatever explanation 

 is given for such abnormal forms of sensation, there can be no doubt that 

 in their vividness and indiscriminative nature they represent some want 

 of higher control. 



All these examples of over-action, associated with gross loss of function, 

 show certain primitive characteristics. They are not fortuitous perversions of 

 a normal function, as some have contended, but reveal to a certain degree the 

 mode of action of the lower centres before they were dominated from above. 

 The reaction is massive and exceeds any normal response, both in vividness 

 and extent ; it is stereotyped, predetermined, and the same manifestations can 

 be evoked from an abnormally wide receptive field. Moreover, it depends 

 less upon the intensity of the excitation than on the amount of surface 

 occupied by the stimulus, provided it is effective. 



Thus, when a portion of the spinal cord is completely cut off from higher 

 control, scratching the sole of the foot, or indeed any part below the level 

 of the lesion, may produce spasmodic movements of the whole lower 

 extremity and even of the abdomen. But this is not the only effect; 

 bladder and rectum can be excited to evacuate their contents prematurely, 

 and a profuse outburst of sweating be evoked by any nocuous stimulation. 

 With the return of signs indicating that the higher centres again exert 

 their influence on the lower end of the spinal cord, this want of differentia- 

 tion ceases ; scratching the sole of the foot no longer produces an effect 

 upon the bladder and rectum, and the form assumed by the muscular 

 response again begins to depend upon the situation and nature of the 

 stimulus. 



In the same way, on the afferent side, any effective stimulation of a 

 protopathic area causes a vivid diffuse sensation, not uncommonly referred 

 to remote parts at a distance from the place to which it is applied. The 

 " more or less-ness " of the response is determined to a greater degree by the 

 extent of the stimulus than by its intensity. The end-organs of the punctate 

 system in the skin act as a warning mechanism; any form of excitation 

 capable of producing a sensation leads to a highly impulsive but feebly dis- 

 criminative reaction. 



The abnormal vividness of a protopathic response applies not only to 



Q 2 



