Mich. Comp. Laws § 141.15

Sec. 5. The county treasurer shall have custody of all moneys, securities and evidences of debt belonging to or pertaining to said sinking fund, and he shall pay out the moneys of said fund only by order of the board of sinking fund commissioners by a 2/3 vote of the members thereof as aforesaid, and upon the warrant of the chairman of the board of supervisors, countersigned by the clerk. The official bond of the county treasurer shall cover any and all funds in his hands belonging to the sinking fund.