The origin and progress of the title of cardinal may be found in Themassin, (Discipline de l'Eglise, tom. i. p. 1261 - 1298,) Muratori, (Antiquitat. Italiae Medii Aevi, tom. vi. Dissert. lxi. p. 159 - 182,) and Mosheim, (Institut. Hist. Eccles. p. 345 - 347,) who accurately remarks the form and changes of the election. The cardinal-bishops so highly exalted by Peter Damianus, are sunk to a level with the rest of the sacred college.