Where county boundaries are changed, as hereinbefore provided, and a part of a county or a borough becomes part of another county, if the county to which said part of a county or borough is transferred constitutes a city the part or borough so transferred shall become a part of the city and be subject to the government of the city, and the local government theretofore existing shall cease, and the property and assets of such local government or of the school district thereof shall become the property and assets of the city and the city school district to which it is attached.
16 P.S. § 7177