1. INTRODUCTION
Having had under treatment a typical case of that type of fragilitas ossium which is commonly called "brittle bones and blue sclera," I am in a position to describe for the first time the pathology of the condition, and to add certain clinical observations to those which are included in the rather extensive literature on the subject.The term "fragilitas ossium" is loosely applied to conditions that are characterized by an abnormal fragility of the bones. Bone fragility may be congenital or acquired, and may be due to developmental defects or to local or general absorption of the mineral constituents of normal bone. It is one of the most obscure subjects in modern medicine. The terminology is confused and the pathology is not well understood.Our knowledge is particularly vague in regard to the so-called idiopathic or developmental types of bone fragility. This includes three fairly well defined