Definition of Mediastinum. Mediastinum: The area between the lungs. The organs in the mediastinum include the heart and its large veins and arteries, the trachea, the esophagus, the bronchi, and lymph nodes. Search MedTerms:
The Pax Romana ended because the Roman state had ceased to grow. Boundaries had been set for the Empire, and for the first time the army had become a drain on the econom â¦ y of Rome. Till this point the army provided new slaves and riches from conqured countries.
The Pax Romana was not immediate, despite the end of the civil wars, because fighting continued in Hispania and in the Alps. Nevertheless, Augustus closed the Gates of Janus (the Roman ceremony to mark world Peace) three times, first in 29 BC and again in 25 BC.