Joseph McKenna, Industrial Accident Commission of California v…
“ Commerce is movement, and the work and general repair shops of a railroad, and those employed in them are accessories to that movement, indeed, are necessary to it, but so are all attached to the railroad company, official, clerical or mechanical. Against such a broad generalization of relation we, however, may instantly pronounce, and successively against lesser ones, until we come to the relation of the employment to the actual operation of the instrumentalities for a distinction between commerce and no commerce. ”
