Although there is no useful method of treatment, prophylaxis is possible and valuable. It consists in preventing the development of tæniæ in farm and sporting dogs. For this purpose it is sufficient to prevent their obtaining raw offal containing vesicles of echinococci from sheep, oxen, or pigs, and also to free them from any helminths which they may harbour. In this way they no longer spread eggs of tæniæ with their fæces in the neighbourhood of ponds or drinking places, and the cattle do not ingest the embryos. SUPPURATIVE ECHINOCOCCOSIS. =Causation.= Simple echinococcosis may remain undetected for a long time, and young animals affected with it may grow up without exhibiting marked general disturbance. The old echinococci end by degenerating, the wall of the cyst becomes modified, the liquid it contains, turbid, lactescent, then caseous; the vesicle becomes wrinkled, and finally nothing resembling the primary vesicle remains. The liquid is soon absorbed, and the primary cyst is only represented by a caseous magma, which undergoes calcareous infiltration and progressive atrophy. Under other circumstances the development of the echinococcus vesicles is less regular; they may become accidentally infected and transformed into encysted abscesses, constituting suppurative echinococcosis of the liver. The membrane of the vesicles usually resists the passage of microbes, but the fibrous tissue surrounding the cyst is very vascular; and if, in consequence of vascular disturbance in the liver (which may result simply from feeding, trifling infection or other visceral disease), the blood should for a short time be infected, microbes penetrate through solutions of continuity in the wall of the vesicle, which becomes a centre of suppuration. The liquid becomes turbid, the primary cyst is transformed into an abscess, and suppurative echinococcosis is set up. =Symptoms.= The general condition resulting from the development of suppuration in echinococcus cysts is very different from that of true echinococcosis. If the abscess develops rapidly, acute generalised peritonitis or localised peritonitis of the right anterior abdominal region may almost immediately occur, producing all the characteristic symptoms of ordinary peritonitis. In all cases, even in the absence of well-marked peritonitis, perihepatitis occurs, and the liver becomes adherent to the posterior surface of the diaphragm, to the hypochondriac region, to the abdominal wall, or to one of the gastric compartments. This perihepatitis is indicated by exceptional sensitiveness in the right hypochondriac region, and by respiratory disturbance due to fixation of the diaphragm.