of rhythm forms.  On the one hand, there is a progressive refinement in the discrimination of variations from temporal uniformity as the series of stimulations advances; and correspondingly, the sequence of motor reactions presents a clearly marked increase in cooerdination taking place parallel with its progress.  A rhythmical form is thus given to the whole succession of simple measures which are included within the limits of the larger series, a form which is no less definite than that exhibited by the intensive and temporal relations of the rhythmical unit, and which, there can be little doubt, is even more important than the latter in determining the character of the rhythm experience as a whole.

The presentation of experimental results bearing on this point will follow the lines already laid down.  Only that part of the material which is derived from the apprehension of sensory rhythm forms can be applied to the determination of this formal curve for the ordinary metrical types and their complications.  The facts of progressive cooerdination presented by beaten rhythms are based on the repetition of simple forms only.  The completion of the evidence requires a quantitative analysis of the temporal relations presented by the whole sequence of integrated measures which compose the common verse forms:  dimeter, trimeter, etc.  This matter was not taken up in the present investigation.

The perception of variations in the measures of an iambic pentameter line was first taken up.  The series of sounds was produced by the fall of hammer, the distances traversed being, for the accented elements 0.875 inch, and for the unaccented, 0.250 inch.  The series was followed by a pause equal to one and a half measures, and was repeated before judgment was made.  The time occupied by the series of sounds was 2.62 seconds.  The intervals between the successive sounds were adjusted on the basis of previous experimentation concerning the most acceptable relations between the durations of accented and unaccented intervals.  Their values were in the ratio 1.000:0.714 for accented and unaccented respectively.  The variations were introduced in a single element, namely, the interval following the accented beat of the group, which, in this form of rhythm, is also the inter-group interval.  This interval was changed by successive increments of one seventh its original value, or one twelfth the duration of the whole measure.  Four such additions were made, the final value of the interval standing to its original duration in the ratio 1.000:0.636.  The same series of changes in the duration of the accented interval was made successively in each measure of the pentameter series.  In all these experiments the subjects were in ignorance of the character and position of the changes introduced.  The results appear in the annexed table.

TABLE LVIII.