His conduct 315 He defeats the Barbarians 316 The depraved Commodus 316 His vices 316 Is assassinated 316 CHAPTER XLII. FROM PERTINAX TO DIOCLETIAN. A.D. 192-284. Pertinax made emperor 319 Is assassinated 319 Didius Julianus 319 Severus 320 His severe rule 320 Geta and Caracalla 321 Papinian executed 321 Cruelties of Caracalla 322 Elagabalus 322 Alexander Severus 322 Maximin 323 The Goths invade the empire 324 Valerian 325 Thirty tyrants 325 Zenobia 325 Aurelian 325 The Emperor Tacitus 326 Frugal habits of Carus 326 CHAPTER XLIII. FROM DIOCLETIAN, A.D. 284, TO CONSTANTINE'S DEATH, A.D. 337. Diocletian 327 His colleagues 328 Persecution of the Christians 329 Abdication of Diocletian 329 Constantine the Great 330 His administration 331 The Council of Nice 332 Constantinople 332 Its magnificence 333 The praefectures 334 Christianity the national religion 334 Taxes 334 Family of Constantine 335 He is baptized and dies 335