Phrasing has always been an essential factor of musical performance. However, in the course of time, both the approach to it and the system of indicating it have undergone many changes. The use of slurs to indicate phrasing, which is common practice today, only became possible when the slur was no longer needed for marking legato. In the 18th century, legato was still conveyed by slurs and the whole concept of phrasing was quite different. Musicians tended to think less in terms of long phrases, and were inclined to dissect them into smaller units of one or two bars. These were called "Einschnitte", a term which occurs frequently in the theoretical works of the 18th century.
Unlike the cadence, the Einschnitt never occurred at the end of a phrase.
Johann Adam Hitller, Anweisung zum musikalisch-richfigen Gesange, 1774 (p. 143, § 8):
". . . Now I shall have to tell my singers something about the term Cadence. . . . This term actually means a conclusion in music. Nowadays there is a distinction between perfect a imperfect cadences; the latter are also called Einschnitte, since they occur from time to time in the course of a melody but never at the end. The complete cadence, however, concludes a piece or one of its main sections."
Before Hiller's time there were hardly any marks or signs to help the musician to find such units or Einschnitte, and neither Hiller nor other writers mention such signs. But it seems that at about this time composers began to indicate Einschnitte by the notation itself. These attempts are explained in a long article on performance in J. G. Sulzer's Allgemeine Theorie der schönen Künste, 1771-4 (p. 1250, art. "Vortrag"):
"All the Einschnitte must be observed (marquirt) most clearly and precisely. The Einschnitte are the commas in a melody which, as in speech, must be conveyed by a short rest. This can be done by a brief pause on the last note of a phrase and by starting a new on the first note of the next phrase; or by slightly reducing the volume of tone of the last note and resuming it with the first one of the next phrase. (The term 'phrase' is used here in its widest sense, referring to Einschnitte, sections and periods) . . .
"If the phrase does not end with a short rest, greater skill is