De Schweinitz defined phthiriasis palpebrarum (phthiriasis ciliorum, blepharitis pediculosa, pediculosis ciliorum) as that condition which "occurs when the pediculus pubis or crab louse forsakes its seat of predilection and finds a habitat among the eyelashes."
According to Ball,1 this condition "is uncommon in this country." Schwenk,2 however, reported having personally observed 20 cases among 20,319 patients at the dispensaries of the Wills and Pennsylvania Hospitals in Philadelphia, during ten years' clinical service, the ratio being 1:1,016 patients. He further stated: "I think the infrequency of these cases is greatly overrated. Hirschberg reports having seen only three cases in 40,000 patients. Despagnet reports only two cases in twelve years in the large clinic of Galezowski. There are two cases out of 10,000 cases reported by Dr. de Schweinitz as having been seen in Dr. Norris's clinic at the Hospital of the University of Pennsylvania. Julien . . . says that it