=Epidemiology.=—There is a consensus of opinion that every case of leprosy owes its origin to contact, direct or indirect, with some other case, but evidence as to the manner in which the disease is transmitted, or even the proof of transmission, is to a great extent lacking. Every book refers to the inoculation experiment by Arning, of a freshly excised leprous nodule sewn into a skin incision of the arm of a condemned criminal. In this case a neuritis developed shortly after the inoculation and the patient showed fully developed leprosy three years later. Unfortunately for the value of the experiment the man was a native of Hawaii and had lepers in his own family. Against this experiment are the numerous instances where physicians have inoculated themselves and others with leprous material with invariably negative results. Danielson inoculated himself and nine others with leprous material and later Profeta repeated the same, but without success in a single instance. As regards those living for a long time in attendance on lepers there have been a very few instances of the contraction of leprosy as in the case of Father Damien at Molokai, and two instances in Sisters of Mercy. Such cases however are most exceptional, as the hundreds of attendants on the unfortunates continue their work for years without showing any signs of leprosy. It is stated that there has never been an instance of transmission of leprosy to any attendant at the Saint Louis Hospital, Paris. There are two cases which show that those who live in close relation to lepers may develop the disease; in one, a leper returned to Ireland and his brother, who had never been in a leprosy country, but who had occupied the same bed with the leper and worn his clothes, developed the disease in about five years. A similar case is reported from Germany. As showing that even with intimate contact, infection is rare, it is stated that of 225 healthy Hawaiians, living in the same houses with lepers, only 4½% contracted leprosy. Even when married to lepers only 9 out of 181 healthy people contracted leprosy from their leprous mates. In Japan, 7% of children of lepers contract the disease, 3.8% of those married to lepers and 2.7% of people living in the same house with lepers. Just as with tuberculosis, in which all evidence points to the predominance of infection in early life and its infrequency in adult life, so does it seem to be true of leprosy. Among 10,000 lepers in the Culion leper colony, Denny notes that 35% were brothers and sisters, 27% were cousins, 11% were children of lepers, 7% parents of lepers, and only 1% husband and wife. This would indicate that the relationships involving intimate contact in childhood are etiologically most important.