2529. The ancients recognized both ascending and descending rhythms
(2528), and regarded the former class as at least equal in importance to
the latter; but many modern scholars since the time of Bentley have
preferred to treat all rhythms as descending, regarding the first arsis
of an ascending rhythm as merely answering to a preliminary upward beat
in music. Such an initial arsis was named by Gottfried Hermann
_Anacrūsis_ (Gr. ἀνάκρουσις, _a striking up_).
Scholars have been influenced to adopt the anacrustic theory in its
widest extent largely by the fact that in most modern music a measure
must commence with a downward beat, a rule which did not hold in ancient
music. By this theory an iambic verse becomes trochaic with anacrusis,
an anapaestic verse dactylic with anacrusis, &c. But in many cases those
kinds of verse which begin with an arsis were subject to different rules
of construction from those which begin with a thesis. Hence it seems
best to restrict anacrusis to logaoedic verse, in which it undoubtedly
occurs.
2530. The anacrusis may be a long syllable, a short syllable, or two
shorts (but not two longs). It is often irrational (2524). In metrical
schemes it is often set off from the rest of the verse by a vertical row
of dots: thus, ⁝