Hydrocephalus, an accumulation of fluid within the cavity of the skull, either in the ventricles of the brain or in what is known as the subarachnoid space. Acute hydrocephalus is caused by inflammation of the membranes which enclose the brain. [Meningitis.] Chronic hydrocephalus is usually a disease of intra-uterine life or of early childhood, and as it thus develops before the vault of the skull has become completely ossified, the accumulating fluid distends the yielding cranial bones and produces great deformity; the forehead protrudes, the eyes are pushed forwards, and the enlargement of the skull is in marked contrast to the emaciated face and puny frame of the affected subject. The mental condition of the child suffers, as might be expected, from the damage which results to the central nervous system, convulsions are not infrequent, and the child rarely lives more than two or three years. In some instances, however, the disease becomes arrested, and the patient may live to adult age. Little can be done in the way of treatment beyond the adoption of palliative measures, and the promotion of the general nutrition.