This rhythm (Prescott)

Strong and unrestrained emotion expresses itself in waves, with a throbbing or pulsation, in recurrent movements appearing in voice and gesture, which constitute a natural rhythm. Poetry, an emotional expression, has this rhythm. The beat of a passage of poetry or impassioned prose is not a superadded ornament, but an inevitable and vital accompaniment of such expression, going back, we may imagine, for its origin to the poet's heart.

F. C. Prescott, Poetry and Dreams