PART VII 

 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 proprioceptive 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 stimulation 

 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 consciousness they are contrasted with the sensa- 

 tions arising from the other sense organs in the same way as they are in the 

 subconscious regulation 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 \\c 

 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. 



VOLITIONAL MOVEMENTS. Consciousness we have seen to be 

 developed in proportion to the differentiation of the educatable associa- 

 tion centres, which are responsible for our powers of ideation, and 

 by means of which the different reflex movements which we call 

 volitional are carried out, guided, augmented, or inhibited, according 

 to the past experience of the individual. Volitional movement is there- 

 fore a movement determined by previous neural events, of which a part 



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