12. The common law defence of non est factum to actions on specialities in its origin was available where an illiterate person, to whom the contents of a deed had been wrongly read, executed it under a mistake as to its nature and contents, he could say that it was not his deed at all . In its modern application, the doctrine has been extended to cases other than those of illiteracy and to other contracts in writing. In most of the cases in which this defence was pleaded the mistake was induced by fraud ; but that was not, perhaps, a necessary factor, as the transaction is “invalid not merely on the ground of fraud, where fraud exists, but on the ground that the mind of the signor did not accompany the signature; in other words, that he never intended to sign, and therefore, in contemplation of law never did sign, the contract to which his name is appended”