but they are fixed functions of the dynamic values of these elements and units.  Two identically figured groups (e.g., | >q. q q | >q. q q | ), no more possess rhythmically substitutionary values than does the opposition of a single beat to an extended series (e.g., | >q. | >q. q q | ), apart from this factor of temporal proportion.  Those groups which are identical in figure must also be uniform in duration if they are to enter as substitutionary groups into a rhythmical sequence.[5] When the acatalectic type is alternately departed from and returned to in the course of the rhythmical sequence, the metrical equivalents must present total time-values which, while differing from that of the full measure in direction and degree, in dependence on the whole form of their structure, maintain similar fixed relations to the primary type.  The changes which these flexible quantities undergo will here only be indicated.  If the substitutionary groups be of different figures, that which comprises the larger number of elements will occupy the greater time, that which contains fewer, the less.

[5] Theoretically and strictly identical; this abstracts from the cooerdination of such identical groups as major and minor components of a higher rhythmical synthesis, which is really never absent and in virtue of which the temporal values of the groups are also differentiated.

I do not forget the work of other observers, such as Bruecke, who finds that dactyls which appear among trochees are of less duration than the latter, nor do I impugn their results.  The rhythmical measure cannot be treated as an isolated unit; it must always be considered in its structural relations to the rhythmical sequence of which it forms a part.  Every non-conforming measure is unquestionably affected by the prevailing type of the rhythmical sequence in which it occurs.  Bruecke points out the converse fact that those trochees and iambs are longest which appear in dactylic or other four-measures; but this ignores the complexity of the conditions on which the character of these intrusive types depends.  The time-values of such variants are also dependent on the numerical preponderance of the typical form in the whole series.  When a single divergent form appears in the sequence the dynamic relations of the two types is different from that which obtains when the numbers of the two approach equality, and the effect of the prevailing form on it is proportionally greater.  Secondly, the character of such variants is dependent on the subordinate configuration of the sequence in which they appear, and on their specific functions within such minor rhythmical figures.  The relative value of a single dactyl occurring in an iambic pentameter line cannot be predicated of cases in which the two forms alternate with each other throughout the verse.  Not only does each type here approximate the other, but each is affected by its structural relation to the proximately higher