SENSATIONS OF MOVEMENT AND POSITION 601 



sheath and, after making many spiral turns round the muscle fibres, branch 

 freely and terminate in little knobs on the surface of the fibres (Figs. 310,311). 

 The cross-striation of the muscle fibres within the spindle is but faintly 

 marked. It is evident that the continuity of these sense-organs with the 

 contracting muscle ensures in the best possible way that the organs should 



pr.e. 



FIG. 310. A neuro- muscular spindle of the cat. (RUFFINI.) 

 c, capsule ; pr.e, primary ending ; s.e, secondary ending ; pl.e, plate ending 

 (all these are probably sensory in function). 



FIG. 311. Part of a muscle- spindle more highly magnified. 

 n, nerve fibres passing to spindle ; a, annular endings of axis cylinders ; s. spiral 

 endings ; d, dendritic endings ; sh, connective-tissue sheath of spindle. (RUFFINI.) 



be affected by the slightest change of tension of the muscle, and should 

 transmit information of the state of tension to the central nervous system: 



THE PSYCHOLOGICAL SIGNIFICANCE OF SENSATIONS OF MOVE- 

 MENT. Not only are these organic sensations of importance as affording 

 us information of the condition of our own bodies as distinct fronrthe objects 

 in the world around, but they enter into and qualify our judgments derived 

 from all the sensations which arise in the special sense-organs. 



When we regard the continuous aimless activity of a healthy baby, we 

 see that all ideas of space, of extension, of relative position are wanting, or at 

 any rate are not present to guide the movements. Bit by bit muscular 

 experience is acquired. The child learns that a given movement of the right 

 arm will bring the hand in contact with something which is exciting the left 



