HYDATIDS IN THE ABDOMINAL VISCERA. 161 



admit of the supposition that the tumour had opened 

 into the serous cavity of the abdomen or of the 

 chest. 



When a hydatid cyst opens into a cavity invested 

 by mucous membrane, the hydatids are expelled, 

 either whole or in fragments, by expectoration, or by 

 vomiting, or with the evacuations, or the urine. In 

 the present place we need only consider those cases 

 in which the hydatids, having penetrated the alimen- 

 tary canal, are discharged by vomiting or with the 

 evacuations. 



The opening of communication which is formed 

 between the hydatid cyst and the intestines is 

 generally very narrow, and permits only of the very 

 slow discharge of the vesicles, so that their expulsion 

 from the body occupies a considerable period, some- 

 times extending over several months. The perforation 

 is not always sufficiently large to allow of the com- 

 plete emptying of the cyst, which may then open 

 into some other viscus, or at the surface of the body. 



The passage of the contents of the cyst into the 

 alimentary canal does not give rise to inflammation 

 of the mucous membrane, and the only effect pro- 

 duced by it is usually diarrhoea, which is sometimes 

 very difficult to control. 



The opening of a cyst into the intestines may be 

 known by the sensation of internal rupture which 

 the patient often experiences, by the rapid subsidence 

 of the tumour, and by the expulsion through one of 

 the outlets of the body of vesicles, which are either 

 whole or in fragments, and are recognisable by the 

 naked eye or with the aid of the microscope, and which 

 sometimes contain the booklets of the echinococci. 



M 



