This classification undoubtedly forms a practical basis on which to estimate the feasibility of operative measures, and it would appear that sincipital and small occipital cephaloceles are the only cases that come within the realms of operative treatment. In estimating the possibility of operation, however, due consideration must be paid to the fact that, in the very great majority of cases, the tumour tends to increase in size, the bones become further thinned, the margins of the gap more everted, and the development of the brain suffers correspondingly. Again, in spite of the fact that some few cases have survived to adult age, yet it is the general rule for the patient to die within a few weeks or months of birth. For desperate ills, corresponding measures must be undertaken, and in the consideration of the more serious cases the surgeon should be biased in favour of operation unless the general condition of the child shows clearly that no success is possible. The best results have been attained in cases of pure meningocele. =Operation.= The unhealthy condition of the overlying integument, especially at the apex of the tumour, prohibits any extensive preparatory cleansing, this process being carried out for the most part when the child is under the anæsthetic. Scalp-flaps are framed from the region of the base of the tumour, advantage being taken of the more healthy parts. These flaps must be so sized and framed that accurate approximation and complete covering to the gap will be attained at the termination of the operation. The flaps are dissected back to their base. The pedicle of the tumour is defined and an endeavour made to detach it completely from the margins of the osseous defect. This is often a matter requiring considerable patience. The sac of the tumour should then be tapped with trocar and cannula, and the fluid contents allowed to escape slowly, after which the opening into the sac is enlarged and the membranes slit up towards the base of the protrusion. When dealing with a pure meningocele, the membranous protrusion is cut away in such a manner that sufficient tissue is left to allow of closure of the dural gap. This closure can be carried out either by means of a purse-string suture or by the union of two lateral flaps. In either case, accurate approximation is essential in order to prevent as far as possible the further escape of cerebro-spinal fluid. If the sac should contain an irregular mass of neuroblastic and mesoblastic tissue, apparently not true cerebral or cerebellar substance, this material can be dissected from the membranous sac, ligatured at its base, and freely cut away.