39. Also the detainer of a man’s person by virtue of lawful process or authority; actual imprisonment. .In a sentence that the defendant “be in custody until,” ete, this term imports actual imprisonment. The duty of the sheriff under such a sentence is not performed by allowing the defendant to go at large under his general watch and control, but so doing renders him liable for an escape. Smith v.. Com., 59 Pa. 320; Wilkes vy. Sluugbter, 10 N. C.