μήτρα, in poetry, a system of feet of a just length.

The different metres in poetry, are the different manners of ordering and combining the quantities, or the long and short syllables: thus hexameter, pentameter, iambic, sapphic verses, &c. consist of different metres, or measures. See HEXAMETER.

In English verses, the metres are extremely various and arbitrary, every poet being at liberty to introduce any new form that he pleases. The most usual are the heroic, generally consisting of five long and five short syllables, and verses of four feet, and of three feet, and a caesura, or single syllable.

The ancients, by variously combining and transposing their quantities, made a vast variety of different measures, by forming spondees, &c. of different feet. See POETRY, no. 124, &c.

METRORODUS, a Greek physician, born at Chios, was the disciple of Democritus the philosopher, and the master of Hippocrates the physician and Anaxarchus the philosopher. He maintained, that the universe is infinite and eternal: but his works are lost. He lived about 444 B.C.