Section 49. For section 68 of the principal Act, the following section shall be substituted, namely:

49. For section 68 of the principal Act, the following section shall be substituted, namely:— "68. An assignment of a patent or of a share in a patent, a mortgage, licence or the creation of any other interest in a patent shall not be valid unless the same were in writing and the agreement between the parties concerned is reduced to the form of a document embodying all the terms and conditions governing their rights and obligations and duly executed."