Powerful friends are never superfluous, and Cardan seems to have needed them in Rome as much as in Bologna. In 1573 he again hints at plots against his life, but almost immediately after recording his suspicions he goes on to suggest that his danger had arisen chiefly from his ignorance of the streets of Rome, and from the uncouth manners of the populace. "Many physicians, more cautious than myself, and better versed in the customs of the place, have come by their death from similar cause." The danger, whatever its nature, seems to have threatened him as a member of the practising faculty at Rome rather than as the persecuted ex-teacher of Pavia and Bologna. Rodolfo Sylvestro was not the only one of his former associates near him in his old age, for he notes that Simone Sosia, who had been his _famulus_ at Pavia in 1562, was still in his service at Rome. In reviewing the machinations of his enemies to bring about his dismissal from the Professorship at Bologna, Cardan indulges in the reflection that these men unwillingly did him good service, that is, they procured him leisure which he might use in the completion of his unfinished works, and in the construction of fresh monuments which he proposed to build up out of the vast store of material accumulated in his industrious brain. The literary record of his life in Rome shows that this was no vain saying. He was at work on the later chapters of the _De Vita Propria_ up to the last weeks of his life; and, scattered about these, there are records of his work of correction and revising. While telling of the books he has lately been engaged with, he wanders off in the same sentence to talk of the dream which urged him to write the _De Subtilitate_, and of the execution of the _Commentarii in Ptolomaeum_, during his voyage down the Loire. In 1573 he seems to have found the mass of undigested work more than he could bear to behold; for, after making extracts of such matter as he deemed worth keeping, he consigned to the flames no less than a hundred and twenty of his manuscripts.[239] Before leaving Bologna he had put into shape the _Proxenata_, a lengthy collection of hints, maxims, and reflections as to everyday life; he had re-edited the _Liber Artis Magnae_, and had added thereto the treatise _De Proportionibus_, and the _Regula Aliza_. He also took in hand two books on Geometry, and one on Music, and this last he completed in 1574. On November 16, 1574, he records that he is at that moment writing an explanation of the more abstruse works of Hippocrates, but that he is yet far from the end of his task.