DEVELOPMENT OF EMBRYO. 79 



can the inner wall of the Echinococcus-vesicle give rise to the 

 same phenomena as are elsewhere exhibited by the serous inner 

 wall of the cysts? The latter certainly appears improbable, and 

 we may, perhaps, corne nearest to the truth if we suppose, either 

 that after death the wall of the Echinococcus allows the passage 

 of the purulent mass secreted by the serous wall of the cyst, or, 

 which appears to me most probable, that the Echinococcus-vesicle 

 is ruptured in particular places, that the pus passes through 

 these into the cavity of the vesicle, that from its contents pro- 

 teinaceous detritus, calcareous matter, and cholesterine are 

 deposited, and that the scolices and hooks which have been set 

 free are enveloped in these masses. In the pig, at any rate, 

 I have found pus-globules between the cyst and the vesicle, in 

 places where these had separated from each other after the death 

 of the worm. Whoever knows how difficult it is to separate 

 the worm and its cyst during life, and how rarely this is done 

 without tearing, will not consider that I am going too far with 

 my supposition of the secondary entrance of the pus into the 

 inner cavity of the worm after its death through the cracks 

 produced during its collapse. The daughter- and granddaughter- 

 vesicles appear to be capable of continuing their existence 

 after the death of the mother-vesicle, and the latter are usually 

 without pus, calcareous masses, and the like, when they are in 

 good preservation and have no openings. The enveloping cyst 

 presents the same phenomena as that of the Cysticerci, especially 

 of Cyst, tenuicollis. 



In referring to pathological death we have still to notice the 

 artificial pricking of the embryonal vesicle which has become 

 developed into a cystic worm. We are aware, from the experi- 

 ments in the cure of Ccenurus by puncture, that the thin-walled 

 forms, after their vesicles have been punctured, become com- 

 pletely collapsed and destroyed in consequence of the injury. 

 In Echinococci, for example, in the kidney, in which I have seen 

 daughter- and granddaughter-vesicles pass off, and then again an 

 entire cessation at various intervals, a cure appears to be capable 

 of taking place. Mb'ller has very recently seen the undisturbed 

 growth of a punctured Echinococcus. 



We now come to the question of what further becomes of the 

 resting scolex of the cysticercal, platycercal, and acercal Cestoid 

 forms of the third stage of development ? In answering this ques- 

 tion we are led to the consideration of 



