536 GENERAL ANATOMY. 



I. OF VESICULAR WORMS. 



847. Vesicular worms,* Entozoa cystica, (Rud.) con- 

 sist in great part, of a caudal vesicle more or less voluminous, 

 peculiar to a single or common to several worms: the body is 

 depressed or rounded, always very small; the head (wanting 

 in one genus) is furnished with pits (two or four,) with suckers 

 (four,) with a crown of hooks or of four recurved probosces; 

 there is no visible intestinal canal or genital organs. These 

 worms inhabit always the substance of the organs in a distinct 

 cyst; they have been confounded together for a long time, and 

 with cysts, under the name of hydatids. Even now natural- 

 ists reject one or two genera from this order, which consists 

 of the following: JLcephalocystis, Echinococcus, Cysticerus, 

 and Diceras. 



848. The acephalocystis,t a genus established by Laen- 

 nec, but not adopted by Rudolphi, or by Cuvier, consists in 

 a vesicle, without head or body, round or obround, from the 

 size of a little pea to that of a middling apple, with thin and 

 soft, transparent, whitish, homogeneous, fragile walls, filled 

 with a limpid, aqueous, and albuminous fluid. It is doubtful 

 whether spontaneous movements have been observed in it. It 

 appears that these equivocal beings reproduce by interior buds. 

 They have been met with in almost all the organs. Seven or 

 eight species are known. They are always encysted, if we 

 except the clustered mole, which is regarded as the result of 

 the reunion or of the suture of one species of this genus. 



849. The echinococcus, a genus of Rudolphi, which com- 

 prehends perhaps the acephalocystis,and which Cuvier does not 

 admit, consists in a simple or double external vesicle, to the 

 internal surface of which are attached several worms, fine and 

 granulated like grains of sand, whose body is ovoid, and the 

 head (like that of the armed tsenia) furnished with a crown of 

 hooks and suckers. 



* T/aennec, Memoire sur les vers veslculaires, &c., in the Bulletin de fEcok 

 de medicine. Paris, an. xiii. 



f Laennec, he. tit. Ludersen, .Diss. dc hydalidibus; (Jotting 1 ., 1808. 

 H. Cloquet, Faune de mcdecins, torn. i. Paris, 1- 



