Every railroad corporation shall cause a good and sufficient brake to be attached to every car used upon its railroad for the transportation of passengers or freight, except four wheeled freight cars used only for transporting freight and shall cause to be stationed on every passenger train trusty and skillful brakemen, equal in number at least to one for every two cars in the train, except on passenger trains on which power brakes are used, and one such brakeman upon the last car of every freight train, which must always be equipped with a good and sufficient brake.