The salaries of county commissioners, payable by their respective counties in full for all services performed by said commissioners except as otherwise provided, shall be as follows:—
Middlesex............................$9,505.16
Essex............................8,799.73
Norfolk............................8,799.73
Worcester............................8,799.73
Bristol............................7,388.87
Hampden............................7,388.87
Barnstable............................6,683.44
Berkshire............................6,683.44
Plymouth............................6,683.44
Franklin............................5,272.58
Hampshire............................5,272.58
Dukes............................2,963.90