“ It was there said (p. 150) : 'There can be no doubt that a right of recovery thereunder arises only where the injury is suffered while the carrier is engaged in interstate commerce and while the employee is employed by the carrier in such commerce.' Again (p. 152) : 'The true test always is: Is the work in question a part of the interstate commerce in which the carrier is engaged?' And a like view is shown in other cases. ”

“ And oftentimes, following the movement of cars, loaded or empty, to a given point, other cars were gathered up and taken or started elsewhere. In short, the crew handled interstate and intrastate traffic indiscriminately, frequently moving both at once and at times turning directly from one to the other. ”

“ When loaded the freight in them was at times destined from within to without the state or vice versa; at other times was moving only between points within the state, and at still other times was of both classes. When the cars were empty the purpose was usually to take them where they were to be loaded or away from where they had been unloaded. ”