The brain and its meninges participate, in many respects, in the changes worked by rachitis, and mainly in the abnormal vascularization of the bones. They are very much congested, and succulent. A section through the brain shows a great many large and small blood-points. This hyperæmia may give rise to over-nutrition, which assumes the character of real hypertrophy of the brain. When that hyperæmia, however, becomes excessive, effusion will take place into the cavities, the tissue of the arachnoid, and the substance of the cerebrum, which latter looks {149} peculiarly brilliant, elastic, and sometimes white, in consequence of the blood-vessels being emptied by the pressure on the part of the enlarged mass of the cerebrum upon the blood-vessels. Thus, instead of cerebral hyperæmia there may be anæmia. Every form of hydrocephalus may follow the rachitical process. Afterward, when the craniotabes has healed, the secondary effusions will generally also disappear, but not a few cases of hydrocephalus may be traced to rachitis occurring during the first half year of life. When that occurs, the intellectual faculties may suffer, while, on the contrary, complete recovery not infrequently exhibits an unusual degree of mental development, for the same reason which improves the chances of the development of the bone. The degrees of physiological and pathological nutrition and over-nutrition are very variable in their nature and results. This condition of the cranial contents is not the only one brought about by rachitis. The softness of the cranial bones permits a direct pressure on the brain. The side on which the infant for the most part reposes gets flattened, and the brain is also compressed. The skull consequently bulges out in the opposite direction. This anomaly, as stated above, is sometimes visible through life, though in the large majority of cases after recovery from rachitis has taken place this asymmetry will gradually disappear. Before that can occur, however, the infant is liable to suffer from the rachitical changes. Convulsions are by no means rare. Vogel has, however, been able to produce an attack of convulsions by pressing upon the softened spots of the cranium. Permanent or temporary contractures of the fingers and toes I have seen in several instances. Gerhardt looks upon rachitis as one of the causes of tetany.