Mass. Gen. Laws ch. 35 § 2
In any county, except Suffolk and Nantucket, the county treasurer may appoint an assistant in his office, who has served therein for at least one year, as assistant treasurer, removable at his pleasure. The assistant treasurer shall give bond, and the provisions of the second sentence of section three shall apply to such bond.
If the treasurer is unable to act, the assistant treasurer shall perform his duties. If both the treasurer and the assistant treasurer are unable to act, the county commissioners may appoint a temporary treasurer, who shall hold office until the treasurer or assistant treasurer is able to resume his duties. The temporary treasurer shall give bond, and the provisions of the second sentence of section three shall apply to such bond.
Mass. Gen. Laws ch. 35, § 2