_Of Concussion._—Concussion, in a greater or less degree, attends most injuries of the head. The functions of the brain are either disturbed or suspended; there is loss of sensibility, of volition, and frequently of the power of motion. The confusion of intellect or stunning may disappear in a short time, or may continue, though diminished in intensity, for many days, and even for weeks; it is seldom, however, that the functional disorder exceeds in duration two or three days, and in general it disappears before that length of time has elapsed. The stupor is seldom complete; the patient can perhaps be roused, though with difficulty, so as to answer questions by a hurried monosyllable, or make signs in regard to the seat of pain, or for such things as he may suppose himself to be in need of. At first the circulation is weak; the pulse is fluttering, often intermitting, and scarcely to be felt in the extremities; the countenance is pale, and the surface cold; there is occasional vomiting, a symptom which seldom occurs when compression of the brain exists, and the breathing is difficult, though scarcely ever stertorous. The pupils are generally contracted, but not uniformly so; one pupil may be contracted and the other dilated; at first, they are insensible to light, neither dilating when in darkness, nor contracting further when the light is suddenly increased; not unfrequently a considerable degree of squinting exists. The muscles are neither much relaxed, nor spasmodically contracted. After a time, the circulation is restored, and the heat of the surface returns, with more or less of regained sensibility. The pulse either becomes altogether natural, or else more slow or more rapid than in health. The circulation is then easily excited; by even raising the patient in bed, the pulsations of the carotids are increased, in some cases, by fifteen or twenty beats. Sensibility returns, always very gradually, and in some cases more slowly than in others; frequently the patient becomes quite collected after the lapse of some hours or a few days, but in other instances a degree of mental confusion remains for many weeks; occasionally the intellect continues weak for a lengthened period, and sometimes even for the remainder of life.