For services as an officer of an institution district, each commissioner, the controller and the treasurer in second class counties shall receive an additional annual salary of two thousand five hundred dollars ($2500) and each commissioner of a seventh class county shall receive an additional annual salary of eight hundred dollars ($800) and each commissioner of an eighth class county shall receive an additional annual salary of three hundred dollars ($300). In every other county the commissioners, and the treasurer, shall receive no additional compensation for services to the institution district. In every county the commissioners and treasurer shall be allowed their necessary expenses incurred in services for the institution district. Every county controller in office on September twenty-nine, one thousand nine hundred fifty-one, shall receive during the remainder of his current term an allowance for expenses incurred in connection with the institution district as follows: (1) In second class counties, two thousand dollars ($2000) per annum; (2) In third class counties, eighteen hundred dollars ($1800) per annum; (3) In fourth class counties, fifteen hundred dollars ($1500) per annum; (4) In fifth class counties, twelve hundred dollars ($1200) per annum; (5) In sixth class counties, one thousand dollars ($1000) per annum.