T^NIA ECHINOOOOCDS. 261 



A. ovis tragelaphi, Cobbold. 



Vesicarla granulosa, Sciirank. 



Hydatigena granulosa, Batsch. 



Hydatis, Ludersen ; Rudolphi ; Olfers ; Bremser ; etc. 



H. erratica, Blumenbacli. 



The employment of these various names radicates that their 

 several authors, until quite recently, recognized in the hydatid an 

 independent and specifically distinct organism ; and it seems not 

 a little humiliating for us now to have to declare our persuasion 

 that the forms here named are one and all of them larval conditions 

 of the Httle Tcenia echmococcus of the dog and wolf. But so it is ; 

 and whilst the mature worm has thus a very limited territory for 

 its place of residence, its pecuHar larvee, on the other hand, are 

 found dwelling in a great variety of animals. Amongst the bearers 

 are men, monkeys, sheep, oxen, deer, camels, the girafie, and other 

 ruminants ; also the horse, ass, zebra, several fehne animals, 

 and, perhaps, the squirrel. Yon Siebold also described an example 

 of Echinococcus jfrom the lung of a turkey. 



Hydatids present very variable appearances according to their 

 situation and mode of formation ; thus, we have three principal 

 kinds which may be severally described as exogenous, endogenous, 

 and multilocular. The first kind are sparingly found in man, but 

 are extremely common in the lower animals, whilst the second is 

 most fi:-equently developed in the human subject, the third kind 

 being, I believe, only found in man. The two first forms some- 

 times coexist in the same bearer, though I have not myself 

 witnessed any instance of this. Instances of the kind are recorded 

 by Haen, "Wunderlich, and Davaine.* In the lower animals 

 hydatids generally occur in the form of single globular or lobulated 

 cysts, varying in size from a wahiut to that of the egg of a goose. 

 Usually there are several cysts occupying the same organ, or, not 

 imfrequently, several organs in the same bearer. As Livois has 



* Eeferences to these cases are given by Leuckart in a footnote (l. c. s. 365). 



