Her husband felt vexed,--and especially as he wished to impose upon her understanding,--that with all his powers of speech, and his assumption of profound knowledge, he could not now, any more than hitherto, succeed in converting her to the faith which he himself pretended so devoutly to hold, that lunatics sometimes could not be known by their conversation, and that the individual James Woodruff, in particular, who was the subject of their conversation, was actually as mad as a March hare, notwithstanding the actions and appearances, undeviating and regular, which in his case so obstinately forced upon Mrs. Rowel the private conviction that he was quite as sound in intellect as any other subject within the King's dominions. Nevertheless the doctor stifled the feelings of petulant resentment which were rising in his bosom, and satisfied himself simply by assuring his good, though somewhat perverse lady, that it was no very unusual thing for a certain description of lunatics to maintain their own sanity by arguments which, in any other case, would be considered very excellent; though, with experienced professional men, that very fact went farther in support of their derangement than almost any other that could be brought to bear. “Whenever,” continued the doctor, with some degree of warmth, “whenever I meet with a patient,--never mind whether he is under medical treatment or not,--a patient who endeavours by argument and proof to show me that he is _compos mentis_,--who seeks for evidence, as it were, in his own mind to substantiate the sanity of that very mind,--that is, a man who appeals for proof to the very thing to be itself proved,--who tests the mind by the mind,--when I meet with a patient of that description, it seems to imply a kind of doubt and distrust of his own intellect, and I set him down, in spite of what anybody can say to the contrary, as _non compos mentis_, and a proper subject on whom to issue a writ _ideota inquirendo vel examinando_.” “I cannot argue with you like that, Frank,” observed the doctor's wife; “but do you mean to say that a man cannot himself tell whether he is mad,--and that nobody else, by what they see and hear, can tell either?” “I do!” exclaimed Rowel. “I contend that numberless instances exist of latent mental derangement, which are totally unknown both to the insane themselves, and to those persons who are about them.” “Then how do _you_ know it?” asked the lady. “From the very nature of things, my dear,” Mr. Rowel replied. “Time was when verdicts of _felo de se_ were returned in cases of self-destruction; but now every twopenny shopkeeper is wise enough to know, that the very act of self-murder itself is evidence of mental derangement.” “But what has this to do with the question?” demanded Mrs. Rowel.