"While the ministry flourishes in the Church, it (the Church) ought indeed to use it (the ministry) in the calling of pastors, nor can pastors be ordinarily instituted except by a ministry already constituted " (says Turrettin).
(source - p. 270 - no specific citation to Turretin)
Turrettin lays it down that "the pastors exercise the right which belongs to the body, as representing it, and in such away that that right always belongs radically to the body;" and again, "when a ministry is wanting or miserably corrupt, the Church, can elect for itself ministers for its edification even without the intervention of a ministry; as well both because this right it has from God, as because always and everywhere it is bound to preserve a ministry" tenetur ministerium conservare.
(source - p. 275 - no specific citation to Turretin)
Nevertheless, it appears that these translations may be gathered from Part III, Locus XVIII, Question XXV, items XVIII-XIX of Turretin's Institutes of Elenctic Theology (link).
I thought it worth pointing out that Turretin leaves open the possibility of ministers being ordained from non-ministers - i.e. ordination by the flock, rather than by the shepherds. I'm not sure what Turretin's Biblical warrant for this is - but perhaps the warrant is simply this: it is necessary that there be elders - and the specifically provided-for way of ordination is the preferred way they be appointed. Nevertheless, ordination is not something magical - necessarily requiring a chain of hand on head contact going back to Christ.