Any description of the pathology of amebiasis must pay tribute to Councilman and Lafleur,1who in 1891 first described the lesions in detail and differentiated them from the lesions of bacillary dysentery, and to Leonard Rogers,2Kartulis,3Kuenen,4Craig,5James6and many others who have made contributions to the subject since that time. The action of Endamoeba histolytica is fundamentally the same in all the tissues that it invades and in all susceptible animals into the tissues of which it gains entrance. This action is based on two weapons of attack possessed by the ameba; namely, mechanical invasion by means of pseudopods and a toxin that acts directly on the tissues of the host. With these facts in mind it is possible to trace the development of amebic lesions wherever they occur and to understand the fully developed picture that is usually seen in