THE EXERCISES 163 The above method of procedure reaches a pitch of exactitude which in itself is very interesting. IMPRESSION OF FORM THROUGH TOUCH ALONE (EDUCATION OF THE STEREOGNOSTIC SENSE) To recognize the form of an object by feeling it all over, or rather touching it with the finger-tips (as the blind do) means something more than exercising the tactile sense. The fact is that through touch one perceives only the super- ficial qualities of smoothness and roughness. But, whilst the hand (and the arm) is moving all round the object, there is added to the tactile impression that of the movement carried out. Such an impression is attributed to a special sense (a sixth sense) which is called the muscular sense, and which permits many impressions to be stored up in a * muscular memory/ or a memory of movements accomplished. It is possible for us to move without touching anything and to be able to reproduce and remember the movement made, with regard to its direction, the limits of extension, etc. (a pure con- sequence of muscular sensations). But when we touch something as we move, two sensations are mixed up together—tactile and muscular—giving rise to that sense which the psychologists call the " stereognostic sense ". In this case, there is acquired not only an impression of movement accomplished, but knowledge of an external object. This knowledge may be integrated with that gained through vision, thus giving a more concrete exactness to the perception of the object. This is very noticeable in little children who seem to be possessed of greater certainty in recog- nizing things, and above all greater facility in remembering them when they handle them than when they only see them. This fact is made evident by the very nature of the children in their early years. They touch everything they see, obtaining the double image (visual and muscular) of the innumerable different things with which they come in contact in their environment.