Page:Mind (New Series) Volume 15.djvu/86

 72 HENRY RUTGERS MARSHALL : In accordance with the symbols of section 8 we will then have, in five successive moments, presentations which may be represented as follows : (1) Pl~2_3"4 5 > _pl~2_34 5. (5) |,i. But, of course, cases where the stimulus acts for an in- definitely short time may really be eliminated from our con- sideration. They do not actually occur in our experience, and therefore the presentations corresponding with them do not occur. They have been spoken of merely to prepare the way for the study of the actual cases now to be mentioned. Where the stimulus acts not merely for an indefinitely short time ; but where, as is normally the case, it is con- tinuous for a sufficient time to act in relation with the rhythm of activity within the system ; then in successive moments we will have, in the first place, a slight change in the reaction upon the continuing stimulus from moment to moment due to the fact that the nature of the system is altered at each moment as the result of the reception of the stimulus ; and this we may indicate by placing different Greek letters over the large P's used in the symbols. In five successive moments, therefore, under a perfectly continuous stimulation we will have five primary presentations which we may symbolise thus : {pi - 2 _ 34 5 I I pi _ 2 _ 34 5 I J pi _ 2 _ 34 5 I a ' ( 1 ft ' f^l y ^l-2_34 5j l p l 2_34 5j (^,1 2 _ 34 Q 5 J etc., etc. But beyond this in each successive moment after the first the primary presentation will be complicated by the secondary presentations due to effects of the preceding moments of stimulation. Consequently in five successive moments we shall have five forms of presentation which may be sym- bolised as follows: 2 _ 34.