Prior to the latter part of the seventeenth century any bony or stony mass in the body, regardless of its origin, nature or location, was called a "stone," and if perchance it was apparent in or beneath the skin, it was designated a "skin stone." These masses were classified according to their consistency, color, configuration, size and weight.
In 1683, Fred Slare,1 chemist of the Royal Society of London, inaugurated the chemical study of the stones of the human body, thereby differentiating quite correctly from true bone formation the various calcifications, inspissated secretions and deposits of specific salts. His observations were confirmed by Boerhaave.2 However, the absolute diagnosis of bony tissue must be credited to the microscope, which, in a crude form, was coming into use at that time.
According to Sehrt,3 true ossification in the skin may be separated into six distinct groups: