“The dictator, or consul, had a right to command the service of the Roman youth; and to punish an obstinate or cowardly disobedience by the most severe and ignominious penalties, by striking the offender out of the list of citizens, by confiscating his property, and by selling his person into slavery. The most sacred rights of freedom, confirmed by the Porcian and Sempronian laws, were suspended by the military engagement.”