From this comes the synthetic power of the rhythm.  Just as the simple unit groups are built up by this synthesizing power, so they in turn are combined into larger phrases and periods.  The motor factor has little place in Wundt’s own discussion,[7] the ‘mental activity’ is the all-important thing.  Bolton[8] also made a very important contribution to the experimental knowledge of rhythm.  His work was based entirely on Wundt’s theory.  His method of experimentation was accurate and his observations copious.  The arrangement of his apparatus, however, led him to emphasize objective uniformity as a condition of rhythmic grouping; so that Meumann’s criticism of his application of this principle to poetry is quite just.  Nevertheless Bolton established the essential facts of subjective accentuation and apparent temporal displacement.  It is noteworthy that he laid great emphasis on the motor aspect of rhythm, and made many careful observations on the ‘motor accompaniment.’  While inclining strongly to a motor interpretation he did not attempt to cut loose from the Wundtian ‘apperceptive process’ as the primary factor.

   [6] Wundt, W.:  ‘Physiol.  Psych.,’ 4te Aufl., Leipzig, 1893, Bd. 
   II., S. 83.

   [7] Wundt, W.:  ‘Physiol.  Psych.,’ 4te Aufl., Leipzig, 1893,
   II., S. 89 ff.

   [8] Bolton, T.L.:  Amer.  Jour. of Psych., 1894, VI., p. 145 et
   seq.

The most elaborate consideration of rhythm yet published is that of Meumann.[9] He avowedly worked out and defended the theory of Wundt.  The only important difference is the larger place which he gave to the ‘motor accompaniment,’ although he was always careful to emphasize its secondary and derived character.  He insisted that the ’mental activity’ is always primary, and that without it there can be no rhythmization; and he opposed vigorously the motor inclinations of Mach and Bolton.  It is certainly unfortunate that rhythm has always fallen into the hands of the investigators of the ‘attention,’ or the ‘span of consciousness,’ or the ‘perception of time.’  It is but an incident that judgments of time are often based on rhythms; and everything that Meumann has said of a ‘mental prius,’ or a ‘synthesizing activity’ in the case of rhythms, may just as well be said in the case of any cooerdinated act.

   [9] Meumann, E.:  Phil.  Stud., 1894, X., S. 249 ff.

Meumann discussed in detail the characteristics of the rhythm of a simple series of sounds, of music, and of verse.  He assumed that in the simple sound series we have rhythm in its barest form, and only the rhythmic synthetic activity is at work; while in music there is a content which to some extent prescribes unities, and the objective regularity of the rhythm is broken.  In verse we have much more content, and the rhythmization is no longer regular in its temporal relations; it is entirely dominated at times by the ‘logical unities’ of the ‘thought.’