Thus, the foetal and congenital occurrence of rachitis cannot be doubted. Both forms are represented in literature. Neither requires the presence of rachitis in one or both of the parents. But the cause of the intra-uterine disease has not been found. Perhaps a disease of the mother with considerable nutritive disorders or a defective placentar supply may be found responsible. The foetal form runs its course long before the normal termination of pregnancy; the congenital may have run its full course at birth or complete it afterward. The bones are found of characteristic nature, the diaphyses suffering more than the epiphyses; even a rachitical pelvis has been met with by Fischer. Early foetal rachitis is probably dependent upon a defective development of the very first cartilaginous deposits and the first osseous nuclei; thus, many of the congenital synostoses find a ready explanation. Besides these, abnormal circulation is accounted for. For periosteal proliferation at that early period contracts the foramina carrying the blood-vessels, and, while interfering with the size of the bones, the foramen magnum also. Thus, a certain class of cretinism appears to be due to foetal rachitis, mainly of the base of the cranium, which results in early ossification of the synchondroses, particularly of the sphenoid bone. But lately I have seen a case of this description, which, however, had not terminated at the time of birth. For after birth the rachitical process developed further, and in addition to the rachitical deformity of the base of the cranium there were afterward thickening of the epiphyses, pigeon breast, and thoracic grooving and flattening. Rachitis is found in city and country, less on mountains than in valleys. Still, it is met with at elevations of two thousand feet. In the tropical regions it is almost unknown. Why it should have been considered quite a new disease in England but a few centuries ago, or whether it did not exist before that time, it is difficult to say. It is certain, however, that deformities have been described in antiquity which we are accustomed to attribute to rachitis. As the disease is one that occurs during the period of rapid growth, and is a developmental disease, everything that interferes with normal growth and development is apt to change physiological functions into pathological conditions and to produce rachitis. In the pregnant mother her ill-nutrition and the defective cell-material used in the building up of the embryo and foetus, or a defective placenta, may come in for the explanation of foetal and congenital rachitis, although the case of Klein's, who reports twins, of which one was normal and one rachitic, is rather difficult to explain on that basis only. Even rachitis of early infancy is not easily accounted for otherwise, for its first symptoms show themselves at a very early period; thus constipation, adiposity, and afterward craniotabes and thoracic grooving.