THE ORGANIC SENSATIONS 



SECTION XII 

 SENSATIONS OF MOVEMENT AND POSITION 



IN studying the phenomena of reflex movements, as presented by 

 the spinal animal, our attention was drawn to the importance of 

 the afferent impulses transmitted to the central organ by means of 

 a special system of sense-organs, called by Sherrington the proprio- 

 ceptive system. ^These afferent impressions intervene at a later period 

 in every reflex action than do the initiating sensory (exteroceptive) 

 impulses. They arise as a result of the reflex movement itself, and 

 serve to regulate the extent of this movement as well as the co- 

 ordinated changes in the other muscles of the body. Whether they 

 be synergic or antagonistic, the abolition of the impulses arising in 

 this system has an effect similar to that of the destruction of the 

 governor of an engine. The movements excited by peripheral stimu- 

 lation become excessive and conflicting ; there is no longer the give- 

 and-take of the antagonistic muscles surrounding the joint, and the 

 result is a state of disorder and inco-ordination, termed ataxy. 



Of the proprioceptive impulses a certain proportion reach the 

 cerebral cortex and arouse states of consciousness which we speak 

 of as sensations of position, movement, or resistance, and which 

 form the basis of judgments as to these conditions. In conscious- 

 ness they are contrasted with the sensations arising from the other 

 sense-organs in the same way as they are in the subconscious regula- 

 tion of the motor adaptations of the body. All the senses which we 

 have so far considered give us information of things, i.e. of a material 

 world which can affect ourselves, but which we conceive of as existing 

 altogether apart from our sensations of it. Indeed the visual and 

 auditory sensations we project to distances remote from the body. 

 The sensations, on the other hand, which are aroused through the 

 intermediation of the proprioceptive system we refer entirely to 

 ourselves. By them we receive information of the condition of the 

 material ' me,' i.e. of ourselves as things apart from the objects 

 which surround us and the changes in which ordinarily excite our 

 activity. 



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