There has been a great deal written about the origin of the disease in drinking water, various inorganic constituents having been incriminated as factors. In certain places, as Delhi, oriental sore has decreased among the British troops with the discontinuance of the use of water from certain city wells. We know that oriental sore is rather easily inoculable, it having been stated that certain people of Bagdad inoculated their children in order to insure against the possible appearance of the sore on the face with the resulting scar disfiguration. Wenyon found that the virus would not pass through the unabraded skin. The disease is most prevalent about the end of summer and in the autumn. It is a disease of towns. Some have thought that it might be transmitted through the medium of the laundry. Not only can man be infected by inoculation but this is also possible with monkeys and dogs when a scarified area about nose or over eyebrows is inoculated with virus from a sore. The lesions are similar to those in man but last a shorter time. It has been suggested that the dog may be the reservoir of this virus as well as for that of infantile kala-azar. There is some experimental evidence to show that an animal which has recovered from a visceral leishmaniasis is immune to a cutaneous one. There has been an idea that lizards or snakes might serve as the reservoir of virus for oriental sore and that species of _Phlebotomus_ feeding on these reptiles might take in the flagellates and subsequently transmit them to man. Laveran, however, has been unable to infect lizards with _L. tropica_. Patton’s observations point to infection from the crushing of infected sandflies when biting the exposed surfaces of the skin. The natural infection of man with oriental sore produces a rather lasting immunity. As regards the American sores there is a great deal of difference of statement as to the probable transmitting agent. These sores seem to occur in forest regions where clearing of the trees is going on. Infections occur in late summer or autumn. Marshy districts appear to favour infection. Brumpt thinks the fact that dogs, which are susceptible as well as monkeys to inoculation with the American leishmaniasis, are often bitten by ticks without the production of the sore, is against the view that ticks act as transmitting agents. He rather favors a tabanid fly and in a case reported by Darling the patient incriminated a tabanid fly. Five cases are reported by Cerqueira as following the bite of _Phlebotomus lutzi_. The disease seems to occur naturally in the dog in the infected regions. =Pathology.=—In oriental sore there is an infiltration of the corium and its papillae with plasma and lymphoid cells as well as with large phagocytic cells packed with leishman bodies which cells Wright regards as endothelial cells. There is atrophy of the epidermis.