Release of Function in the Nervous System. 185 



effect of the lesion. Secondly, the positive symptoms consisted of that 

 massive overaction spoken of as " spasticity," the result of the unrestrained 

 energy of lower centres. It was not due, as was commonly supposed, to 

 " irritation," but to release of such centres from the control normally 

 exercised over them by those on a higher functional level. 



This doctrine, in its specific application to certain phenomena of hemi- 

 plegia, was widely accepted, especially in England ; but it was not generally 

 applied to the phenomena of nervous disease, and it is still the custom to 

 attribute to " irritation " most of the excessive reactions produced by organic 

 disease or injury. 



All observers are agreed that the various centres of the nervous system 

 form a hierarchy in which some exercise higher functions than the others ; 

 but the idea that an abnormal response may be an expression of the 

 activity of these subordinate centres has not penetrated widely into neuro- 

 logical medicine. The phenomena of disease are thought to be purely 

 adventitious ; they are spoken of as " pathological," and are supj)osed to 

 bear no relation, even remotely, to any mode of response which has pre- 

 viously existed in the individual or the race. 



We believe, on the other hand, that in the gradual evolution of function, 

 the reactions of the lower centres have been changed to suit fresh con- 

 ditions. The more complex an organism, and the more efficiently it responds 

 with discrimination to external forces, the greater will be the need for such 

 readjustment. Older modes of response must be modified or suppressed ; 

 some are utilised in tlie newly acquired complex act, whilst others, under 

 normal conditions, are prevented from playing a part. But wherever 

 diminution or removal of a dominant group of functions leads to an 

 excessive outburst of energy, the more primitive responses have not been 

 abolished ; for had they disappeared completely in the process of evolution, 

 destruction of a higher centre would produce loss of function only, 

 unaccompanied by signs of over-activity. Normally, they are suppressed 

 because they would disturb the more discriminative responses of higher 

 centres ; but they still remain capable of revival under conditions demanding 

 urgent and impulsive action. 



Eelease of function, due to failure of higher centres to exercise normal 

 control, can occur in two ways. Structural changes may so lower their 

 capacity that they can no longer play a dominant part in some complex act, 

 and suppress inappropriate manifestations from subordinate centres. In this 

 case the morbid phenomena consist both of loss of function and over-action. 

 This I shall speak of as " disintegration," for it involves the breaking up 

 of an integrated series of responses. 



