SECTION 1. Section thirteen of Act Numbered Four hundred and thirteen, entitled "An Act providing for the control and management of provincial jails and of the prisoners therein," is hereby amended to read as follows:
"SEC. 13. The provincial board may in its discretion cause any or all able-bodied male prisoners, except such as are held as witnesses or awaiting trial, to work upon any of the public roads or highways or other public works, or to clean, tare for, or repair public buildings and grounds, in the province where such prisoners are confined. Such work shall be done under the direction and control of the officer or officers in change of such works, buildings, grounds: Provided, That while so employed the prisoners shall wear the regular prison garb and shall continue to be sufficiently and properly guarded by the jailor or his deputies, or by the Philippines Constabulary if available for that purpose."