Mass. Gen. Laws ch. 160 § 64
A railroad corporation, unless authorized by the general court or by the six following sections, shall not directly or indirectly subscribe for, take or hold the stock or bonds of or guarantee the bonds or dividends of any other corporation; and the amount of the bonds of one or more other corporations subscribed for and held by a railroad corporation, or guaranteed by it conformably to special authority of the general court or the authority given in said sections, with the amount of its own bonds issued in conformity with sections forty-seven and forty-nine, shall not exceed at any time the amount authorized by said section forty-seven, computed as provided in section fifty-three of chapter one hundred and fifty-nine.
Mass. Gen. Laws ch. 160, § 64