Alexis Thomson,
Manual of Surgery, Sixth Edition…
(1921)
“ Callosities# are prominent, indurated masses of the horny layer of the epidermis, where it has been exposed to prolonged friction and pressure. They occur on the fingers and hand as a result of certain occupations and sports, but are most common under the balls of the toes or heel. A bursa may form beneath a callosity, and if it becomes inflamed may cause considerable suffering; if suppuration ensues, a sinus may form, resembling a perforating ulcer of the foot. ”
