Sec. 2. In making the annual per capita apportionment to the schools of the counties having a population of not less than twelve thousand one hundred (12,100) and not more than twelve thousand one hundred and ninety (12,190), according to the last available Federal Census, the county school trustees shall also make an allowance out of the State and County Available Funds for the payment of the salary of the County Superintendent of Public Instruction, not less than Twenty-one Hundred Dollars ($2100.00) nor more than Three Thousand Dollars ($3,000.00), and an office expense not exceeding Three Hundred Dollars ($300.00) per annum for stamps and stationery, and the Commissioners' Courts of the counties herein affected may expend out of the General Fund of such counties any sums not exceeding Three Hundred Dollars ($300.00) per annum to defray the traveling expenses incurred by said County Superintendent, which said sum shall be paid by said Commissioners' Courts upon certificate of said Superintendent that the expenses have been incurred in the discharge of his duties as such Superintendent.