The structural arrangement of the mineral matters in sedimentary and crystalline pearls

The author began by giving a sketch of what has hitherto been written on pearl structure, and pointed out that since Rondelet threw out the idea that pearls are merely diseased concretions occurring in the Mollasca in the same way as other morbid calculi occur in the Mammalia, and Réaumur said they are misplaced pieces of organised shell, in the same way as loose cartilages in human joints are misplaced portions of the cartilaginous structures surrounding them, the opinions of all subsequent writers have but oscillated between these two antagonistic theories.