(1) In any suit for infringement of a patent, every ground on which it may be revoked under section 64 shall be available as a ground for defence.

(2) In any suit for infringement of a patent by the making, using or importation of any machine, apparatus or other article or by the using of any process or by the importation, use or distribution of any medicine or drug, it shall be a ground for defence that such making, using, importation or distribution is in accordance with any one or more of the conditions specified in section 47.