Section 38B. A prisoner in any jail or house of correction, or in any correctional institution of the commonwealth who commits an assault or an assault and battery upon an officer, guard or other employee of any jail, house of correction or correctional institution or upon any duly authorized officer, guard or other employee of any such jail, house of correction or correctional institution engaged in the transportation of a prisoner for lawful reasons shall be punished by imprisonment in the state prison for not more than ten years. Such sentence shall begin from and after all sentences currently outstanding and unserved at the time of said assault or assault and battery.