6. The =enclosing rhyme=, corresponding to the formula _a b b a_, e.g. in _spray, still, fill, May_, as in the quartets of the sonnet formed after the Italian model (cf. below, Book II, chap. ix). This sort of rhyme does not often occur in Middle English poetry; but we find it later, e.g. in the tail or veer of a variety of stanza used by Dunbar and Kennedy in their _Flyting Poem_. 7. The =tail-rhyme= (in French called _rime couée_, in German _Schweifreim_), the formula of which is _a a b c c b_. (For a specimen see § 79.) This arrangement of rhymes originated from two long lines of the same structure, formed into a couplet by end-rhyme, each of the lines being divided into three sections (whence the name _versus tripertiti caudati_). This couplet, the formula of which was _- a - a - b || - c - c - b_, is, in the form in which it actually appears broken up into a stanza of six short lines, viz. two longer couplets _a a_, _c c_, and a pair of shorter lines rhyming together as _b b_, the order of rhymes being _a a b c c b_. (For remarks on the origin of this stanza see § 240.) § =219.= As to the quality of the rhyme, purity or exactness, of course, is and always has been a chief requirement. It is, however, well known that the need for this exactness is frequently disregarded not only in Old and Middle English poetry (cf. e.g. the Old English assonances meant for rhymes, § 40, or the often very defective rhymes of Layamon, § 45) but even in Modern English poetry. Many instructive examples of defective rhymes from Spenser, Sidney, Shakespeare, and Dryden are given by A.J. Ellis, _On Early Engl. Pronunciation_, iii. 858-74, 953-66, iv. 1033-9. From these collections of instances we see how a class of imperfect rhymes came into existence in consequence of the change in the pronunciation of certain vowels, from which it resulted that many pairs of words that originally rhymed together, more or less perfectly, ceased to be rhymes at all to the ear, although, as the spelling remained unaltered, they retained in their written form a delusive appearance of correspondence. These 'eye-rhymes', as they are called, play an important part in English poetry, being frequently admitted by later poets, who continue to rhyme together words such as _eye: majesty_ Pope, Temple of Fame, 202-3; _crowns: owns_ ib. 242-3; _own'd: found_ id. Wife of Bath, 32-3, notwithstanding the fact that the vowel of the two words, which at first formed perfect rhymes, had long before been diphthongized or otherwise changed while the other word still kept its original vowel-sound. NOTES: [180] The word stanza is explained by Skeat, _Conc. Etym. Dict._, as follows: 'STANZA. Ital. stanza, O. Ital. _stantia_, "a lodging, chamber, dwelling, also _stance_ or staffe of verses;" Florio. So called from the stop or _pause_ at the end of it.--Low Lat. _stantia_, an abode.--Lat. _stant-_, stem of pres. pt. of _stare_.'