16 Pa. Stat. § 4806
All salaries fixed by law, except as may be otherwise provided for herein, shall be paid from the amounts paid into the county treasury from the respective offices, after ascertaining and deducting the amount due the deputies and clerks in each office. If there has not been a sum sufficient, from fees received and paid in or earned and due by the county for services rendered, to pay the full amount of the salary of any officer holding any of said offices, after deducting the amount due the deputies and clerks, such officer shall receive only such proportion of his salary as shall be equal to the aggregate of the net fees received and earned by him, as aforesaid, during his term of office during such month. If the fees in any subsequent month or months shall exceed the amount of the expense and salary aforesaid for such month, the deficit of such salary for such preceding month shall be made up from such excess.
16 P.S. § 4806