Beata Christi custodit mandata in omnibus, Cuius opera refulgent clara inter homines, Sanctumque cuius sequuntur exemplum mirificum, Unde et in cælis patrem magnificant Dominum.... Folio 13, _verso_; AH 51: 340. Here the ignoring of quantities is such as to preclude a _metrum_.[30] But accentual interpretation also is difficult. Read as a _rhythmus_ based on the _Corde natus_ measure,[31] which was frequently thus used later, it moves tolerably in certain stanzas (e.g., 4 and 7), but in others, including the two quoted, intolerably violates word-accent. Read by word-accent as a _rhythmus_ of three stresses, it makes extravagant use of two intervening unstressed syllables.[32] Indeed, without some clearer clue than has yet been offered, we can hardly be sure what measure was intended.[33] Much less should we regard it as representative of the early poetic capacity of _rhythmus_. That capacity is amply vindicated in other hymns of this very manuscript. 1. Iambic Examination of the early hymns measure by measure begins with St. Ambrose, Bishop of Milan at the end of the fourth century. Both his own fame and the recognition of a typical stanza appear in the general use of the adjective Ambrosian to describe many hymns of unknown authorship and sometimes of uncertain date. The canon of his own hymns has, indeed, been determined;[34] but it is less important than his achievement of a type. His answer to a common need established a common form. He had the discernment, first, to select a popular measure often used accentually, and then so to use it as to obey both the popular stress habit and the learned poetic of quantity. That his hymns are valid either as _metra_ or as _rhythmi_ means, though his regard for word-accent shows that he foresaw the latter rendering, that they must have been composed in the former, and probably that time rhythm was still heard in speech. The increase of the stress habit gradually worked a transformation. The regular dactylic close hardly satisfying so short a line, the final syllable, which even in the ancient metric might be long sometimes, came to be stressed always. As a _metrum_ the iambic dimeter ran _Ætērnĕ rērūm cōndĭtŏr_; as a _rhythmus_ it became _Ætérne rérum cónditór_. The effect, though different, is not inferior. For the distinctive verse values of _rhythmi_, heard at their best in later hymns freely so composed, can be discerned even here in the earliest centuries by rendering as _rhythmi_—as in fact they came to be rendered—two of the most familiar hymns taken from the dimeters of Prudentius. Ales diei nuntius Lucem propinquam præcinit: Nos excitator mentium Iam Christus ad vitam vocat. Auferte, clamat, lectulos Ægros, sopores desides: Castique, recti, ac sobrii Vigilate, iam sum proximus.... _Cathemerinon_ i. 1: AH 50: 23.