R. G. Bury, The Symposium of Plato

ἔστι γὰρ ἰατρική κτλ. Cp. (with Poschenrieder) Hippocr. de flat. I. p. 570 K. πάλιν αὖ πλησμονὴν ἰῆται κένωσις: κένωσιν δὲ πλησμονή...τὰ ἐναντία τῶν ἐναντίων ἐστὶν ἰήματα. ἰητρικὴ γάρ ἐστι πρόσθεσις καὶ ἀφαίρεσις, ἀφαίρεσις μὲν τῶν ὑπερβαλλόντων, πρόσθεσις δὲ τῶν ἐλλιπόντων: ὁ δὲ κάλλιστα τοῦτο ποιέων ἄριστος ἰητρός. Also Phileb. 32 A, 35 A for “repletion” and “depletion” in connexion with bodily φύσις: and Tim. 82 A γῆς πυρὸς ὕδατος τε καὶ ἀέρος...ἡ παρὰ φύσιν πλεονεξία καὶ ἔνδεια...στάσεις καὶ νόσους παρέχει.

ὁ διαγιγνώσκων κτλ. In this passage there is a distinction implied between pure and applied ἰατρική, between medicine as a science (ἐπιστήμη) and as an art (τέχνη). διαγιγνώσκω is here used almost in the technical sense of making a medical diagnosis (cp. Hippocr. de nat. hom. 9 τὴν διάγνωσιν... ποιέεσθαι): possibly earlier “Asclepiads” than Hippocrates may have earmarked διάγνωσις as a medical term. Cf. the distinction between κατὰ γνώμην and κατὰ χειρουργίην in Hippocr. de morbis I. 6.