careful and admirable study of West Indian yaws. His inclination is to look upon parangi, coko, and similar Asiatic and Pacific island diseases as specifically different from the African and West Indian disease. Daniels, however— a most accurate observer, who has had extensive experience in Fiji, in British Guiana, and in Africa— shows very clearly that in these places the diseases are identical. Probably the view that certain forms of the parangi of Ceylon are not yaws is likewise incorrect.
It is impossible at the present day to settle the point, but it seems probable that yaws was originally an African disease, and, so far as America and the West Indies are concerned, that it was introduced by negro slaves. In the days of West Indian slavery the specific and infectious nature of yaws was thoroughly recognized. The planters, from economic apart from other considerations, by instituting yaws-houses and similar repressive measures, took much trouble to keep the disease under. Since emancipation has permitted the West Indian negro to revert to some extent to the state of savagery from which he had partly emerged, yaws has again become very prevalent, and is now a principal and loathsome feature in the morbidity of these islands. Yaws is practically confined to the tropics and subtropics, and even there is absent at high altitudes.
Etiology. Contagion and heredity.— As yaws is highly contagious, all circumstances favouring contact with the subjects of the disease favour its occurrence. Simple skin contact does not suffice; a breach of surface is necessary. Probably the virus is often conveyed by insect bites, or by insects acting as go-betweens and carrying it from a yaws sore to an ordinary abrasion, wound, or ulcer. Thus the disease often commences in a pre-existing ulcer. Cases are prone to originate in certain dirty houses, the virus from previous yaws patients seemingly impregnating the floors and walls of the filthy huts in which the latter had resided. In this way the disease may be acquired without direct transference from an existing case.
