There have been recorded here two cases of osteogenesis imperfecta, one of which is of the so called congenital type in that the fractures, which constitute the main and gross evidence of the developmental defect, were present at birth; and the other is of the postnatal variety, retarded in its manifestations until several years after birth. Each case is characteristic of its type, particularly in regard to duration of life. The first patient, with the congenital fractures, died at the age of five months from an intercurrent respiratory disease. This is the usual fate of this class. Seemingly in this group there is not only a lack of resistance in the bones but a wide-spread, dangerous, and usually fatal lack of resistance that results in an early termination of life. The second patient, exhibiting blue sclera and bone fragility, presumably inherited the disease from his father. This boy, unlike the first case and the many reported in the literature, had exceptional fragility of only the tibiae which were the only bones fractured. This fact is difficult to explain, because the roentgenograms showed about the same degree of atrophy in the other bones studied. This patient has done well, and, if he can be guarded through the period of puberty as well as he has been up to now, he will acquire the resistance against fractures that this group is known to obtain in adult life. Furthermore, in this type of osteogenesis imperfecta tarda, the general bodily resistance (It is unfortunately necessary to use such vague terminology is quite satisfactory and gives no reason to anticipate any abbreviation of the life span.

While there is no suggestion, as yet, to explain the primary cause of the disease, we know that the chief change in the bone is a lack of complete development of the various constituents of bone tissue or, as Key describes the lesion, a hereditary hypoplasia of the mesenchyma. There is no specific therapy. Therefore, for the present, it is reasonable and worth while to utilize general therapeutic agents known to improve bone density and strength,—namely, viosterol given by mouth, and exposure of the body to the ultraviolet rays. This treatment was effective in the second case in which, after some months of treatment, the tibiae appeared less flexible than when the boy was first seen. In the first case, which was under the observation of the writer for three months, there was hardly time enough to effect any improvement.