The employer shall be liable for the negligence of employes other than the plaintiff, while acting within the scope of their employment, including engineers, chauffeurs, miners, mine-foremen, fire-bosses, mine superintendents, plumbers, officers of vessels, and all other employes licensed by the Commonwealth or other governmental authority, if the employer be allowed by law the right of free selection of such employes from the class of persons thus licensed; and such employes shall be the agents and representatives of their employers, and their employers shall be responsible for the acts and neglects of such employes, as in the case of other agents and employes of their employers; and, notwithstanding the employment of such employes, the property in and about which they are employed, and the use and operation thereof, shall at all times be under the supervision, management and control of their employers.