148 ENTOZOA FOUND IN MAN. 



When the cyst is large, or when it is situated 

 close to the pleura, the cavity of the latter is gene- 

 rally destroyed, and the serous folds are united 

 together by firm adhesions. In consequence of the 

 obliteration of the cavity of the pleura, the cyst may 

 find its way towards the surface, and open either 

 through the thoracic or the abdominal parietes, or 

 through the diaphragm. 



The hydatids may also escape, through the per- 

 foration of the bronchi ; and the cyst may thus 

 be emptied, and a cure efiected. 



The cavity which remains after the total expul- 

 sion of the hydatids is contracted and cicatrised ; it 

 is usually single, and there does not commonly exist 

 in it, as in tuberculous cavities, any tendency to 

 the formation of new and analogous pathological 

 products. 



If the hydatid tumour is very large, or of long 

 previous duration, it is only emptied gradually, on 

 account either of the induration of its walls, or of 

 the nature of its contents. The patient, becoming 

 exhausted by the sympathetic fever, cough and 

 expectoration, or by some intercurrent affection, 

 probably dies before the pouch is completely closed. 



Hydatids situated in the lungs may also open into 

 the pleura or the pericardium, but this tei-mination is 

 exceedingly rare in consequence of the strong adhe- 

 sions which usually take place between the folds of 

 which those membranes are formed. Death invari- 

 ably follows the discharge of the contents of the cyst 

 into either of these cavities. 



The duration of hydatid tumours developed in 

 the respiratory organs is always considerable. In 



