shows that the pay differentials enjoyed by the senior officers of a 4th-century regiment were much smaller than those of their 2nd-century counterparts, a position in line with the smaller remuneration enjoyed by 4th-century high administrative officials. Regimental and corps commanders The table above indicates the ranks of officers who held a commission (sacra epistula, lit: "solemn letter"). This was presented to the recipient by the emperor in person at a dedicated ceremony. Cadet regimental commanders (protectores) A significant innovation of the 4th century was the corps of protectores, which contained cadet senior officers. Although protectores were supposed to be soldiers who had risen through the ranks by meritorious service, it became a widespread practice to admit to the corps young men from outside the army (often the sons of senior officers). The protectores formed a corps that was both an officer training-school and pool of staff officers available to carry out special tasks for the magistri militum or the emperor. Those attached to the emperor were known as protectores domestici and organised in four scholae under a comes domesticorum. After a few years' service in the corps, a protector would normally be granted a commission by the emperor and placed in command of a military regiment. Regimental commanders (tribuni) Regimental commanders were known by one of three possible titles: tribunus (for comitatus regiments plus border cohortes), praefectus (most other limitanei regiments) or praepositus (for milites and some ethnic allied units). However, tribunus was used colloquially to denote the commander of any regiment. Although most tribuni were appointed from the corps of protectores, a minority, again mainly the sons of high-ranking serving officers, were directly commissioned outsiders. The status of regimental commanders varied enormously depending on the grade of their unit. At the top end, some commanders of scholae were granted the noble title of comes, a practice which became standard after 400. Senior regimental commanders (tribuni comites) The comitiva or "Order of Companions (of the emperor)", was an order of nobility established by Constantine I to honour senior administrative and military officials, especially in the imperial entourage. It partly overlapped with the established orders of Senators and of Knights, in that it could be awarded to members of either (or of neither). It was divided into three grades, of which only the first, comes primi ordinis (lit. "Companion of the First Rank", which carried senatorial rank), retained any value