τᾶς

From LSJ

ταῦτα δηλώσω αὐτός τε νοσήσας καὶ αὐτὸς ἰδὼν ἄλλους πάσχοντας → I shall describe those symptoms, since I myself had the disease and witnessed as well what others were suffering

Source

French (Bailly abrégé)

dor. p. τῆς, gén. sg. de l'article ἡ.