Release of Function in the Nervous System. ■ 187 



below the lesion may participate- in an energetic withdrawal of the foot 

 from harm. 



Still more remarkable evidence of diffusion of afferent impulses within that 

 part of the spinal cord which lies below the lesion is shown by the behaviour 

 of the bladder and rectum. Not only can evacuation be facilitated by 

 pricking the sole of the foot or by any manipulation which produces a flexor 

 spasm, but passing fluid into the bladder or rectum may evoke an upward 

 movement of the toe, accompanied by other flexor manifestations of the lower 

 extremity ([9], p. 467, et seq. Eiddoch [13]). 



This condition has been spoken of as a " mass-reflex," because any afferent 

 excitation below the level of the lesion is liable to produce motor effects not 

 only in the parts normally thrown into action by such a stimulus, but also in 

 organs that do not usually lie within the arc of its reflex influence. The 

 bladder can be excited to action by stimulating the sole of the foot, and 

 movements of the toes can be evoked by filling the bladder with fluid. 



Eemoval of the influence of the higher centres from those of the spinal 

 • cord has led to a condition in which the outbust of energy, produced by 

 appropriate stimulation, is not only excessive but unduly widespread. Judged, 

 however, by the strength of the stimulus, there is nothing to show that thB 

 spinal centres have become more excitable ; but they have been released from 

 control and respond with a more massive and less discriminative reaction. 



It has long been recognised that an apoplexy may be followed by painful 

 sensations of extreme severity on the opposite half of the body. Largely 

 owing to the researches of Dejerine and his co-workers (Dejerine and 

 Egger [1], Dejerine and Eoussy [2]), we now know that the lesion in such 

 cases usually lies within the optic thalamus. Eoussy ([14] and [15]), further 

 elaborating these signs and symptoms, described a "syndrome thalamique 

 five careful post-mortem examinations confirmed his diagnosis, and many 

 others have since been reported which showed the truth of Dejerine's original 

 . generalisation (Long [12], Winkler and van Londen [20], Holmes and 

 Head [10]). 



The optic thalamus is one of the most intricate regions of the central 

 nervous system and, since most pathological conditions in this situation do not 

 produce selective destruction, the clinical picture presented by a thalamic 

 lesion is usually extremely complex. But by a suitable choice of illustrative 

 cases and by analysis of the symptoms they present, it is not difficult to 

 discover the part played by this organ in sensation. (Head and Holmes [9], 

 p. 551, et seq.) 



First, it forms the receptive end-station for all sensory impulses. From 

 this point they start on a fresh course to culminate in two centres, the cortex 



