The amendment was adopted with reference to conditions existing since the foundation of our government, and the term 'involuntary servitude' was intended to cover those forms of compulsory labor akin to African slavery which, in practical operation, would tend to produce like undesirable results. It introduced no novel doctrine with respect of services always treated as exceptional, and certainly was not intended to interdict enforcement of those duties which individuals owe to the state, such as services in the army, militia, on the jury, etc.