HYDATIDS. 63 



examining for such projections the anatomical limits of the lower 

 edge of the lung must be accurately known. The pleural sac 

 intervenes, and irritation of this may induce an effusion which 

 obliterates the domed outline of dulness projecting from the liver. 



The relations of the liver determine to some extent in what 

 directions hydatids of this organ may rupture. Cysts near the 

 upper surface may open into the pleural sac or the base of the 

 adherent lung; bile-stained cysts may then be expectorated. 

 The pericardial sac has also been invaded. In some cases the 

 liver cyst presents through the lateral thoracic wall or in the 

 epigastrium. Cysts which project from the under surface of the 

 liver are liable to rupture into the greater sac of the peritoneum 

 or more rarely into the lesser sac. Some such cysts open 

 directly into the duodenum or into the stomach, where that is 

 closely applied to the under surface of the liver. Kupture into 

 the pelvis of the right kidney may also take place. 



Splenic and renal cysts are uncommon. The former may bear 

 similar relations to the left lung and pleural sac that liver cysts 

 hold to the right ; or they may encroach on the abdominal cavity. 

 Kenal cysts may open into either the large or small intestines, or 

 the peritoneal sac or even the lung, but most commonly tend to 

 discharge into the ureters, inducing renal colic with the passage 

 of cyst fragments, scolices or booklets. 



The omenta, the mesenteries, the subperitoneal tissue of the 

 abdomen and the pelvic connective tissue, including that which 

 forms the basis of the broad ligaments, and that which lies 

 between the bladder and the rectum form favourite sites for 

 hydatids. Cysts may also be found in the connective tissue of 

 the ischio-rectal fossae, of the neck, trunk, and even of the limbs. 



An interesting fact is noticeable in connection with hydatids 

 of the brain. The cysts are mostly in the cerebrum, and are 

 twice as common in the right hemisphere as in the left ; they are 

 rare in the cerebellum. This distribution points to an embolic 

 origin, and conforms to the ordinary distribution of cerebral 

 embolisms. Hydatid cysts of the brain give rise to little or no 

 surrounding inflammation, and are said never to suppurate 



