It is not very certain at what precise time these two studies (or, if we take prosody to be a part of grammar, this joint-study) began to occupy considerable numbers of professional students. But it must have been a tolerably early one, and by degrees the grammarian in his pure function, the scholiast in his applied one, became recognised personages. The profession, so to speak, may be said (according to the common tradition, but with sufficient justice) to have been formally constituted in the third and second centuries [Sidenote: _The Pergamene and Alexandrian Schools._] before Christ, under the patronage of the successors of Alexander at the courts of Pergamus and Alexandria. To these schools belong the famous names of Zenodotus (the earliest, and belonging partly to the third century), of Crates of Mallos, and, above all, of Aristarchus. It is, perhaps, only at first sight surprising that, famous as the names are, they are for the most part names only. Not one single work, nor even any substantial passage of a work, by any of the three masters just mentioned, or by any of their contemporaries or near pupils, has come down to us, save in the case of one pupil of Zenodotus, more famous even than his master, the grammarian Aristophanes. Criticism indeed, it has been said, has, of all literature that is really literature, the most precarious existence. Still, we know a good deal about them from citations, allusions, and discussions in later writers, while of Aristophanes of Byzantium we have a fairly considerable collection of fragments.