Chapter IV.—Concerning the manner of the Mutual Communication Cf. Athan., De Salut. adv. Christi; Greg. Naz., Orat. 38; Greg. Nyss., Contr. Apoll.; Leont., Contr. Nestor. et Eutych., bk. 1; Thomas Aquinas, III., quæst. 16, art. 4, 5..