One of the most pregnant of Brissaud's lessons is devoted to the elucidation of this part of our subject, and we have already made several quotations from it. In many cases he is forced to say, "I decline to hazard a diagnosis when etiology is silent." We too have been face to face with this diagnostic difficulty on several occasions, and it may be instructive to give the details of one or two cases where no definite conclusion could be arrived at. A man thirty-seven years of age had been suddenly seized with facial paralysis on the left side thirteen years before, accompanied after an interval of eight days by bilateral fronto-temporal cephalalgia, nausea, vomiting, and disturbances of vision. These attacks recurred irregularly during the next four years, since when they have ceased, although the palsy persists. Recently the patient woke up abruptly in the middle of the night to find that the left side of the face was in a state of spasmodic contraction, a condition which has continued absolutely without intermission. There is no pain in relation to the spasm, merely a peculiar sensation at the site of the muscular twitches. Of what nature are they? If we analyse the muscular play somewhat more closely, we observe that with the exception of the frontalis all the muscles of the left face, including the platysma, contribute. On a background of more or less permanent contraction are outlined short, incomplete, greatly varying twitches, affecting one muscle after another, and sometimes only a few fibres, in a highly erratic way. The march of the movements obeys no law, either of space or time, nor is there any co-ordination in their activity. That the condition is one of tic, therefore, is scarcely conceivable. No purposive element is discoverable in the phenomena, no systematisation, no expression of emotional excess. All is disorder, confusion, contradiction. We should, accordingly, be content to make a diagnosis of spasm, but an examination of the patient's mental condition must not be neglected, and in this particular case it is very instructive. It appears that his imagination has always been singularly fertile, amounting indeed to eccentricity. The picturesque description he furnished of the unusual sensations in face and neck lent support to the view that his muscular activity was intended, consciously or unconsciously, to free himself from their insistence, so that his grimacing may have been but a gesture of defence. But however much his lack of psychical equilibrium may favour the relegation of his affection to the category of tic, certain considerations make one question the validity of the hypothesis.