Hydatid

(hi'da-tid.) [From Gr. hydatis, a watery vesicle.] (Zool.) A term applied to nearly all kinds of cyst like productions or cystic parasites invading almost any part of the bodies of men, the ox, the sheep, the horse, the pig, ., many of which are now discovered to be larval stages of the Tænia or Tape-worm. They are generally inclosed in an external sac,which is attached to the ti ue of the organ in which it is situated, and which is frequently common to many H., each of which has a distinct envelope. H. sometimes occasion so little inconvenience, that persons, in whom they are discovered after death, have not suspected any disease in the organ in which they are found. On other occasions, they grow rapidly, and cause so much irritation that suppuration is excited in or around the common sac, which may either burst externally, or into a mucous canal or a serous cavity. In the first or second case, the H. will be discharged, and recovery may take place; in the third case, fatal inflammation will ensue. Little can be done for the treatment of this affection, except that occasionally, if the cyst is near the surface, it may be carefully punctured. See TÆNIA. [s. 468]