After his retirement from the situation of a teacher, Quintilian devoted his attention to the study of literature, and composed a treatise on the Causes of the Corruption of Eloquence. At the earnest solicitation of his friends, he was afterwards induced to undertake his Institutiones Oratoriae, the most elaborate system of oratory extant in any language. This work is divided into twelve books, in which the author treats with great precision of the qualities of a perfect orator; explaining not only the fundamental principles of eloquence, as connected with the constitution of the human mind, but pointing out, both by argument and observation, the most successful method of exercising that admirable art, for the accomplishment of its purpose. So minutely, and upon so extensive a plan, has he prosecuted the subject, that he delineates the education suitable to a perfect orator, from the stage of infancy in the cradle, to the consummation of rhetorical fame, in the pursuits of the bar, or those, in general, of any public assembly. It is sufficient to say, that in the execution of this elaborate work, Quintilian has called to the assistance of his own acute and comprehensive understanding, the profound penetration of Aristotle, the exquisite graces of Cicero; all the stores of observation, experience, and practice; and in a word, the whole accumulated exertions of ancient genius on the subject of oratory. It may justly be regarded as an extraordinary circumstance in the progress of scientific improvement, that the endowments of a perfect orator were never fully exhibited to the world, until it had become dangerous to exercise them for the important purposes for which they were originally cultivated. And it is no less remarkable, that, under all the violence and caprice of imperial despotism which the Romans had now experienced, their sensibility to the enjoyment of poetical compositions remained still unabated; as if it served to console the nation for the irretrievable loss of public liberty. From this source of entertainment, they reaped more pleasure during the present reign, than they had done since the time of Augustus. The poets of this period were Juvenal, Statius, and Martial.