The development then of preliterary Latin under the influence of this systematizing, synthetical influence gave rise to literary Latin, while its independent growth more nearly in accordance with its original genius produced colloquial Latin.  Consequently, we are not surprised to find that the people’s speech retained in a larger measure than literary Latin did those qualities which we noticed in preliterary Latin.  Those characteristics are, in fact, to be expected in conversation.  When a man sets down his thoughts on paper he expresses himself with care and with a certain reserve in his statements, and he usually has in mind exactly what he wants to say.  But in speaking he is not under this constraint.  He is likely to express himself in a tautological, careless, or even illogical fashion.  He rarely thinks out to the end what he has in mind, but loosely adds clauses or sentences, as new ideas occur to him.

We have just been thinking mainly about the relation of words to one another in a sentence.  In the treatment of individual words, written and spoken Latin developed along different lines.  In English we make little distinction between the quantity of vowels, but in Latin of course a given vowel was either long or short, and literary tradition became so fixed in this matter that the professional poets of the Augustan age do not tolerate any deviation from it.  There are indications, however, that the common people did not observe the rules of quantity in their integrity.  We can readily understand why that may have been the case.  The comparative carelessness, which is characteristic of conversation, affects our pronunciation of words.  When there is a stress accent, as there was in Latin, this is especially liable to be the case.  We know in English how much the unaccented syllables suffer in a long word like “laboratory.”  In Latin the long unaccented vowels and the final syllable, which was never protected by the accent, were peculiarly likely to lose their full value.  As a result, in conversational Latin certain final consonants tended to drop away, and probably the long vowel following a short one was regularly shortened when the accent fell on the short syllable, or on the syllable which followed the long one.  Some scholars go so far as to maintain that in course of time all distinction in quantity in the unaccented vowels was lost in popular Latin.  Sometimes the influence of the accent led to the excision of the vowel in the syllable which followed it.  Probus, a grammarian of the fourth century of our era, in what we might call a “Guide to Good Usage"[20] or “One Hundred Words Mispronounced,” warns his readers against masclus and anglus for masculus and angulus.  This is the same popular tendency which we see illustrated in “lab’ratory.”

The quality of vowels as well as their quantity changed.  The obscuring of certain vowel sounds in ordinary or careless conversation in this country in such words as “Latun” and “Amurican” is a phenomenon which is familiar enough.  In fact a large number of our vowel sounds seem to have degenerated into a grunt.  Latin was affected in a somewhat similar way, although not to the same extent as present-day English.  Both the ancient grammarians in their warnings and the Romance languages bear evidence to this effect.