=Treatment.= _Indications for operation._ The results obtained by operation for internal hydrocephalus are not sufficiently encouraging to enable the surgeon to urge immediate operative treatment.[15] Still, it is perfectly clear that he cannot possibly carry out surgical treatment with benefit to the patient if the ventricular distension is allowed to progress to such a degree that marked cortical flattening and degeneration occurs. No fixed probationary period can be laid down as a guide, each case must be judged on its own merits. Special attention should be paid, however, to the disks and lower extremities. Any suggestion of optic neuritis or spasticity should be regarded as urgently demanding operative interference. _Lumbar puncture_ cannot be expected to confer other than temporary benefit even under the most favourable circumstances, whilst, in the event of interference in the normal communication between the ventricular and cerebro-spinal spaces, no relief can be anticipated. Connal recommends that lumbar puncture should be carried out daily, or twice daily, over extended periods of time. This operation, however, is by no means devoid of danger, and the results obtained by such treatment are not at all satisfactory. =Operation.= Operations are carried out (_a_) with the object of withdrawing fluid from the distended ventricular cavities (ventricular puncture), and (_b_) to establish a communication, or short-circuit, between the ventricular space and other spaces (ventricular drainage). _Ventricular puncture._ This operation may be carried out through the anterior fontanelle, through the frontal bone, or over the descending cornu of the lateral ventricle. _Through the anterior fontanelle._ The region of the fontanelle is shaved and cleansed in the usual manner, after which the surrounding parts are cut off from the field of operation by a large sheet of gauze or lint, in which a hole is cut sufficing to allow of exposure of the site of election for puncture.