I have mentioned in a previous publication some of the pathologic changes which may appear in a person with hydatid cyst of the liver, especially one affecting the adventitia. I shall now describe some of the clinical forms of hepatic hydatosis, with particular attention to the treatment. In 85 per cent of cases hydatid cyst of the liver is situated in the right lobe; in only 15 per cent is it located in the left. In either location it may have an anterior or a posterior evolution, but a cyst of the left lobe usually directs itself forward (fig. 1) and ends by protruding onto the epigastrium, where it can be reached by a midline laparotomy (see paragraph 1 in section on technic). The most common type of cyst of the liver, i. e., that of the right lobe, may be central or peripheral. If it is central it does