HYDATIDS IN THE ABDOMINAL VISCERA. 159 



undergo, do not present any special character- 

 istics. 



Their pathological phenomena are analogous to 

 those produced by cysts in the liver, with the excep- 

 tion only that the symptoms dependent upon the 

 compression or ulceration of the biliary passages are 

 absent, when the former viscus is concerned : like 

 the corresponding cysts in the liver, hydatids of the 

 spleen displace the neighbouring viscera, invade the 

 thoracic cavity, and give rise to similar complications. 



The diagnostic signs of hydatids in the spleen 

 differ only slightly from those of hepatic hydatids, — 

 the principal points of distinction being as regards 

 the side which is affected, and the absence of biliary- 

 derangement when the spleen alone is affected. 



Hydatids may also be developed in other viscera, 

 or in other regions, of the abdomen. They may be 

 found in some part of the great visceral cavity, not 

 within the peritoneum, but in the areolar tissue, 

 external to that membrane ; they may originate from 

 the internal surface of the abdominal parietes, or 

 from the external surface of the intestines, of the 

 bladder, or some other organ, or in the substance of 

 the omenta or of the mesentery. 



The cyst is invested externally by the peri- 

 toneum, which forms a more or less complete en- 

 velope for it, and it is sometimes detached from the 

 position whence it originally commenced its growth, 

 and is then only kept in position by a small peduncle. 

 Hydatid tumours are more frequently multiple in 

 these situations, perhaps, than in any other parts of 

 the body. They acquire a very large size separately, 

 or by their union may form a considerable mass. 



