special motor memory will be accordingly developed, and the corrected movement executed with ease. But, as I have shown when speaking of the direct combination of the memories, when a sensory memory impression is continually followed by the execution of a certain movement, the one will soon naturally follow the other, at last, without even cognizance of the mind. It will be seen, from this, that the establishment of some special memory impression, to be continually followed by the requisite movement, will be quite sufficient; thus, let the student continually excite some impression, as a number or particular idea, just before the execution of the movement, until it has become properly established.

RULE XXII.—When a movement has to be performed, no idea of negation of some other movement should be allowed to enter the mind.

The advantage of attending to this rule is very great, and the reason for it is shown in the direct combination of memories which occurs when any movement is being acquired. Now, if a sensory impression, which is usually followed by some particular movement, be revived, that movement is very likely to occur, especially if the person be using his muscles at the time. The seat of judgment, reflection, and the other conscious processes of the mind, is in the cerebral hemispheres; the motor memory, except through a sensory impression conveyed to the mind, affords no information of its workings, and so the most curious blunders are made. Thus a man writes a letter, having in his mind the necessity of not making some particular remark, and finds, to his astonishment, on

reading the letter, that he has made the remark, that he has used the affirmative when he intended to use a negative. So instead of allowing an idea of 'I must not do this' to be in the mind, an idea of 'I must do that' should be substituted. This should especially be borne in mind when writing an examination paper. I have heard of some very curious and outrageous blunders, and feel sure that many of them must have occurred in the above way, as there is, usually, not time to read over what has been written; and it is impossible for an examiner to say, in many instances, whether the mistake be due to ignorance or a slip of the pen.

In the same way, if, when a movement has to be corrected, the idea of 'I must not make the old mistake' enter the mind, it is extremely likely the mistake will be made.