11. _Accent in Time of Plautus._--The rules which have been established for the position of the accent in the time of Plautus are these:
(i.) The quantity of the final syllable had no effect on accent.
(ii.) If the penult was long, it bore the accent (_amabamus_).
(a) if the ante-penult was long, it bore the accent (_amabimus_);
(i.) if the ante-ante-penult was long, the accent was on the ante-penult (_amicítia_); but
(ii.) if the ante-ante-penult was also short, it bore the accent (_cólumine, puéritia_).
_Exon's Laws of Syncope._--With these facts are now linked what may be called Exon's Laws, viz:--
_In pre-Plautine Latin_ in all words or word-groups of four or more syllables whose chief accent is on one long syllable, a short unaccented medial vowel was syncopated; thus *_quínquedecem_ became *_quínqdecem_ and thence _quíndecim_ (for the -_im_ see § 19), *_súps-emere_ became *_súpsmere_ and that _sumere_ (on -_psm- v. inf._) *_súrregere_, *_surregémus_, and the like became _surgere_, _surgémus_, and the rest of the paradigm followed; so probably _validé bonus_ became _valdé bonus_, _exterá viam_ became _extrá viam_; so *_supo-téndo_ became _subtendo_ (pronounced _sup-tendo_), *_aridére_, *_avidére_ (from _aridus_, _avidus_) became _ardére_, _audére_. But the influence of cognate forms often interfered; _posterí-die_ became _postrídie_, but in _posterórum_, _posterárum_ the short syllable was restored by the influence of the trisyllabic cases, _pósterus_, _pósteri_, &c., to which the law did not apply. Conversely, the nom. *_áridor_ (more correctly at this period *_aridos_), which would not have been contracted, followed the form of _ardórem_ (from *_aridórem_), _ardére_, &c.
The same change produced the monosyllabic forms _nec_, _ac_, _neu_, _seu_, from _neque_, &c., before consonants, since they had no accent of their own, but were always pronounced in one breath with the following word, _neque tántum_ becoming _nec tantum_, and the like. So in Plautus (and probably always in spoken Latin) the words _nemp(e)_, _ind(e)_, _quipp(e)_, _ill(e)_, are regularly monosyllables.
12. _Syncope of Final Syllables._--It is possible that the frequent but far from universal syncope of final syllables in Latin (especially before -_s_, as in _mens_, which represents both Gr. [Greek: menos] and Sans. matís = Ind.-Eur. _mntís_, Eng. _mind_) is due also to this law operating on such combinations as _bona mens_ and the like, but this has not yet been clearly shown. In any case the effects of any such phonetic change have been very greatly modified by analogical changes. The Oscan and Umbrian syncope of short vowels before final _s_ seems to be an independent change, at all events in its detailed working. The outbreak of the unconscious affection of slurring final syllables may have been contemporaneous.