The _Ars minor_ explained in simple fashion the elements of speech. But the _Institutiones grammaticae_ of Priscian, a contemporary of Cassiodorus, offered a mine of knowledge. Of its eighteen books the first sixteen were devoted to the parts of speech and their forms, considered under the variations of gender, declension, and conjugation. The remaining two treated of _constructio_ or syntax. As early as the tenth century Priscian was separated into these two parts, which came to be known as _Priscianus major_ and _minor_. The Priscian manuscripts, whose name is legion, usually present the former. Diffuse in language, confused in arrangement, and overladen perhaps with its thousands of examples, it was berated for its labyrinthine qualities even in the Middle Ages; yet its sixteen books remained the chief source of etymological knowledge. _Priscianus minor_ was less widely used. The grammarians of the ninth, tenth, and eleventh centuries followed Donatus and Priscian, making extracts from their works, or abridgements, and now and then introducing examples of deviation from the ancient usage. The last came usually from the Vulgate text of Scripture, which sometimes departed from the idioms or even word-forms approved by the old authorities.[179] The _Ars minor_ of Donatus became enveloped in commentaries; but Priscian was so formidable that in these early centuries he was merely _glossed_, that is, annotated in brief marginal fashion. It would be tedious to dwell upon mediaeval grammatical studies. But the tendencies characterizing them in the twelfth and thirteenth centuries may be indicated briefly. The substance of the _Priscianus major_ was followed by mediaeval grammarians. That is to say, while admitting certain novelties,[180] they adhered to its rules and examples relating to the forms of words, their declension and conjugation. But the _Priscianus minor_, although used, was departed from. In the first place its treatment of its subject (syntax) was confused and inadequate. There was, however, a broader reason for seeking rules elsewhere. Mediaeval Latin, in its progress as a living or quasi-living language, departed from the classical norms far more in syntax and composition than in word-forms. The latter continued much the same as in antiquity. But the popular and so to speak Romance tendencies of mediaeval Latin brought radical changes of word-order and style, which worked back necessarily upon the rules of syntax. These had been but hazily stated by the old writers, and the task of constructing an adequate Latin syntax remained undone. It was a task of vital importance for the preservation of the Latin tongue. Word-forms alone will not preserve the continuity of a language; it is essential that their use in speech and writing should be kept congruous through appropriate principles of syntax. Such were intelligently formulated by mediaeval grammarians. The result was not exactly what it would have been