“ Rep. 190: 'If the statute, reasonably interpreted, either directly or by its necessary operation, burdens interstate commerce, it must be adjudged to be invalid, whatever may have been the purpose for which it was enacted, and although the company may do both interstate and local business. This court has repeatedly adjudged that in all such matters the judiciary will not regard mere forms, but will look through forms to the substance of things.'
It may be conceded in a general way that a state may restrict the right of a foreign corporation to sue in its courts. ”

“ We think that when a corporation goes into a state other than that of its origin to collect, according to the usual or prevailing methods, the purchase price of merchandise which it has lawfully sold therein in interstate commerce, it is there for a legitimate purpose of such commerce, and that the state cannot, consistently with the limitation arising from the commerce clause, obstruct or hamper the attainment of that purpose. ”

“ It will be perceived that these are the conditions upon which many of the states permit foreign corporations to engage in business within their limits when no constitutional limitation is involved; that is, when the character of the business is such that the state is free to exclude such corporations or to admit them upon terms acceptable to it. But here the conditions are sought to be applied in a different way and to a different situation falling within the reach of the commerce clause. ”