THE ORGANS OF RESPIRATION, 153 



their contents then escape into the pleura. Acute 

 pain in the side commonly indicates this accident, and 

 is accompanied by a severe and rapidly mortal attack 

 of pleurisy, owing to the inflammation which at once 

 sets in ; in some instances, however, the progress of 

 the malady is less rapid, and a communication may 

 be estabhshed between the pleura and the bronchi, 

 when the signs of pneumothorax will succeed to 

 those of pleuritic effusion. 



An accurate diagnosis of such a complication could 

 scarcely be formed, unless the existence of a hydatid 

 cyst in one of the abdominal viscera had been pre- 

 viously ascertained. 



The cases which have been recorded of cysts of the 

 liver opening into the pleura are much more nume- 

 rous than those of cysts situated in the lungs which 

 have opened into the same cavity ; this greater 

 relative frequency is doubtless due to the fact that 

 intra-thoracic hydatids generally cause adhesions 

 between the two layers of serous membrane, and 

 also, in a smaller degree, to the circumstance of 

 hydatids being more frequent in the Kver than in 

 the lungs. 



When hepatic cysts have formed a communication 

 with the bronchi, the contents of the cyst may be 

 expectorated, and the pouch emptied similarly to the 

 termination which is observed when cysts developed 

 in the lungs open into those passages ; if a means of 

 elimination is thus procured, some hopes of a recovery 

 may be entertained. 



The course and symptoms of such cases are very 

 similar to those which are present when intra-thoracic 

 cysts open into the bronchi ; sometimes a considerable 



