Where, after the commencement of this Act, a patent is granted to two or more persons jointly, they shall, unless otherwise specified in the patent, he treated for the purpose of the devolution of the legal interest therein as joint tenants, hut, subject to any contract to the contrary, each of such persons shall he entitled to use the invention for his own profit without accounting to the others, hut shall not he entitled to grant a licence without their consent, and, if any such person dies, his beneficial interest in the patent shall devolve on his personal representatives as part of his personal estate.