When cooperative tuberculosis eradication shall be taken up in any county as provided for in N.C. Gen. Stat. § 106-336 to 106-350, the county commissioners of such counties shall appropriate from the general county fund an amount sufficient to defray one half of the expense of  said cooperative tuberculosis eradication. (1921, c. 177, s. 11; C.S., s. 4895(k).)