Just before the plague sent him and his family from Florence a most remarkable incident took place. Raphael had painted a celebrated portrait of Pope Leo X. in a group, and the picture belonged to Ottaviano de Medici. Duke Frederick II., of Mantua, longed to own this picture, and at last requested the Medici to give it to him. The Duke could not well be refused, but Ottaviano wanted to keep so great a work for himself. What was to be done? He was in great trouble over the affair. The situation seemed hopeless. It seemed certain that he must part with his beloved picture to the Duke of Mantua; but one day Andrea del Sarto declared that he could make a copy of it that even Raphael himself could not tell from his original. Ottaviano could scarcely believe this, but he begged Andrea to set about it, hoping that it might be true. Going at the work in good earnest, Andrea painted a copy so exact that the pupil of Raphael, who had more or less to do with the original picture, could not tell which was which when he was asked to choose. This pupil, Giulio Romano, was so familiar with every stroke of Raphael's that if he were deceived surely any one might be; so the replica was given to the Duke of Mantua, who never found out the difference. Years afterward Giulio Romano showed the picture to Vasari, believing it to be the original Raphael, neither Andrea nor the Medici having told Romano the truth. But Vasari, who knew the whole story, declared to Romano that what he showed him was but a copy. Romano would not believe it, but Vasari told him that he would find upon the canvas a certain mark, known to be Andrea's. Romano looked, and behold, the original Raphael became a del Sarto! The original picture hangs in the Pitti Palace, while the copy made by Andrea is in the Naples Gallery. The introduction of Andrea to Vasari was one of the few gracious things, that Michael Angelo ever did. About Andrea he said to Raphael at the time: "There is a little fellow in Florence who will bring sweat to your brows if ever he is engaged in great works." Raphael, would certainly have agreed, with him had he known what was to happen in regard to the Leo X. picture. Notwithstanding Andrea's unfortunate temperament, which caused him to be guided mostly by circumstances instead of guiding them, he was said to be improving all the time in his art. He had a great many pupils, but none of them could tolerate his wife for long, so they were always changing.