What has been already said in reply to the first difficulty applies equally to the second. But is it certain that the use of the monogram in question does not go farther back than the time of Constantine? There is good reason to believe that it is by no means certain. In many portions of the catacombs which, undoubtedly, were excavated before the fourth century, tablets have been found most distinctly marked with this form of monogram. Besides, the same form is sometimes found close by other forms which are beyond doubt of most remote antiquity, and this, too, in corridors which, for the most part, appear to have been excavated before the time of Constantine. Examples of this collocation are to be seen in the cemetery of Cyriaca, in that of Maximus, or Saint Felicitas, in the Via Salaria Nuova, in the cemetery of Saint Hypolytus, in the cemetery of Saint Agnes. It is the well-considered opinion of almost all antiquarians, that the use of the monogram alluded to in the difficulty was by no means infrequent at the close of the third and the commencement of the fourth century--that is to say, at the period of the persecution of Dioclesian. 3. The third difficulty denies the supposition that the slight red coating found on the side of the phials, has been deposited there from blood. Some have been bold enough to say that it is due to the Eucharistic species of wine which the vessels once contained, and which gradually dried up; others say that it has been caused by the decomposition of the glass, or that water trickling through the reddish earth has left behind it a coloured sediment upon the vessel's sides. But it results from careful chemical analysis, frequently repeated, that the red coating is due to the presence of the colouring matter of the blood, and not to any of the causes above recited. The opinion which ascribes it to the Eucharistic species is, above all others, singularly destitute of proof from history or monuments. Since the publication of the Decree we have given above, an important discovery has been made in the Basilica Ambrosiana of Milan, which goes far to justify the accuracy of the decision of the Sacred Congregation. In the year 386 Saint Ambrose discovered at Milan the relics of the two illustrious Milanese martyrs, Saints Gervasius and Protasius. He caused them to be translated to the Basilica, and buried them beneath the altar, on the right or Gospel side. "This spot", said he, in his discourse on the occasion, "I had destined for myself, for it is meet that the bishop should repose where he was wont to offer the Divine Sacrifice. But to these sacred victims I give up the right portion". Saint Ambrose died in 397, and was buried on the left or Epistle side of the same altar, beneath which he had placed the bodies of the holy martyrs.