. . "PART XV A???ENDMENTS OF PATENTS AND APPLICATIONS 83. 11J In any proceedings before the court in which the validity of a patent is put in issue??? the court may??? subject to section 84??? allow the proprietor of the patent to amend the sp.ecification of the patent in such manner??? and subject to such terms as to the publication and advertisement of the proposed amendment and as to costs??? expens" . . .