HYDATIDS. 129 



frequently found scattered throughout the substance 

 of old cysts ; these deposits have a bony appearance, 

 and are composed of phosphate, together with a 

 small proportion of carbonate, of lime. They do 

 not invade the waUs of the tumour in an uniform 

 manner ; sometimes the walls are thin and almost 

 transparent in certain parts, and thick and fibro- 

 cartilaginous in others; whilst in other instances, 

 again, they may have become almost completely 

 osseous. As has been pointed out by Dr. Budd, 

 there is a greater tendency to the deposition of earthy 

 matter in the cysts which occur in old people than in 

 those which occur in younger persons. 



The cyst may become united to the adjacent 

 parts, sometimes by very loose areolar tissue, with 

 blood-vessels ramifying in it, and sometimes by con- 

 densed fibrous tissue, which forms firm adhesions, 

 which can only be destroyed with much difiiculty. 



When the hydatids are developed upon the siu*- 

 face of an organ, in the sub-serous areolar tissue, it 

 may happen that the cyst pushes aside the serous 

 membrane, by which it is partially invested, and that 

 it only remains held in relation with its point of 

 origin by a more or less elongated and slender stalk. 



The internal surface of recent hydatid cysts is 

 white, and smooth, and resembles, to a certain 

 extent that of a serous membrane ; in old cysts, it is 

 roughened, and covered with thick exudations, whilst 

 the vessels sometimes present a varicose appearance, 

 or are surrounded by sanguineous effusions. 



The hydatid cyst is generally of a globular form, 

 and either smooth, or irregularly nodulated, but it is 

 rarely composed of distinct cells ; this latter appear- 



K 



