In the recording of deeds, mortgages, wills or other instruments required or authorized by law to be recorded, the clerk, register of deeds and mortgages, surrogate or other officer required to make the record, shall, in addition to the other indexes made and kept by him, make and keep such classified, analytical or combination index as the board of chosen freeholders of the respective counties shall determine, in index books to be provided for that purpose by the board of chosen freeholders, and shall enter therein, according to the classification thereof, an index of all the names required to be indexed in the alphabetical indexes of their respective offices.