Under the heading of “Injury before Mental Symptoms” it is desirable to consider first the surgical conditions of concussion, cerebral irritability and states of compression with their associated mental symptoms, for these must form a solid background for our consideration of all those cases where there is a head injury and mental disorder supervenes. It is, of course, possible to get an unrecognized fracture of the skull following a slight injury which will cause no further disturbance than, say, a headache. An example of this is supplied in a recent report, where a prospective member of Parliament sustained a fissured fracture of the skull as a result of bumping his head against the roof of a car when going over a hump-backed bridge; but nevertheless went about his business for a month afterwards, ignorant of the fact of the fracture, although experiencing a headache, which eventually sent him to a doctor who, by radiography, was able to make the diagnosis.