620 



VAKIOTJS FOEMS OF ECHINOCOCCUS. 



of this work. I have now, however, come to a different conclusion. 

 For although the formation of peripheral daughter-bladders is to be 

 observed in the hydatidose Echinococcus, this takes place only in con- 

 nection with the multiplication of the hydatids, while they originate 

 by a different mode, namely, the heads and brood-capsules (which we 

 have shown to be morphologically equivalent to the bladders), undergo 

 a retrograde metamorphosis, in consequence of which they assume the 

 form and structure of daughter-bladders. 



Bremser, v. Siebold, and Wagener had previously asserted such a 

 transformation in regard to the head, and Eschricht in regard to the 

 brood-capsules, but, the detailed proof being wanting, their statements 

 did not meet with the consideration which they deserved. But this 

 gap has been iilled up by the publications of Naunyn and Easmussen, 

 and the origin of the organs in question has been sufficiently estab- 

 lished. I must add, however, that Easmussen differs to some extent 

 from Naunyn, inasmuch as he maintains that only the brood- 

 capsules wander about in the daughter-bladders, and denies that the 

 heads have this capability. But according to my own observations 

 he is mistaken on this point. In the Uchinococcus of the sheep, I have 

 observed that the processes referred to by Naunyn may occur exactly 

 as he has described. In the Echinococci of this animal the occurrence 

 of secondary hydatids is by no means so rare as is generally supposed. 

 Naunyn also made his investigations principally on the Uchinococcm 

 of the sheep, but was at the same time convinced that in the human 

 Uchinococcus the hydatids originate in exactly the same way. 



Among the countless heads which are found in the larger Echino- 



coccMS -bladders, partly in the interior of 

 the brood-capsules, and partly free in the 

 fluid of the bladder, one not unfrequently 

 notices some which are modified in a 

 peculiar manner. They are more trans- 

 parent and larger than the others, and in 

 the inflated hinder part of the body 

 contain a cavity filled with -a. clear fluid, 

 through which a distinctly fibrous band, 

 which not unfrequently encloses vessels, 

 runs towards the heads. The character 

 of this cord seems to favour the supposi- 

 tion that it has originated by separation 

 from the middle layer. On the inner 

 surface of the body-wall, which accord- 

 ingly ought to correspond to the peri- 

 pheral layer of the body, are seen the ciliary lappets previously 

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Pia. 331. — Metamorphosis of an 

 Echinococcus-heaA into a bladder in 

 the interior of the brood-oapaule. 

 After Naunyn. (x 60.) 



