STRUCTURE OF THE YOUNG ECHINOCOCCUS. 595 



If developed at all, the young Ecliinococci ought, according to my 

 calculations, to have already measured several millimetres, but I 

 sought in vain in the liver, lungs, and other organs for any such 

 structures. The only phenomena which I could at all connect with 

 the experiment were some small knots resembling tubercles (perhaps 

 1 mm. in size), which shone through the serous covering of the liver 

 in various places. When on the point of concluding that I had again 

 experimented in vain, I discovered in the interior of these knots a 

 spherical body like a bubble, which, in spite of its insignificant size 

 (0'25-0*35 mm.), could be nothing else than a young Ecliinococcus. 



When I first saw it, I almost believed it to be a mammalian egg. 

 A thick, homogeneous, and transparent capsule (0'02-0'05 mm. thick), 

 enclosed somewhat coarsely granular contents, 1 just as the zona pel- 

 lucida encloses the yolk granules. And just as the mammalian egg lies 

 embedded in the cells of the discus proligerus, the outer surface of 

 the clear capsule was surrounded by a substance, in which, upon 

 closer investigation, one could also discern a cellular texture. 



Nothing suggested that it was an animal that lay before me. 

 Being motionless, and devoid of any trace of internal or external 

 organs, it would have been difficult to recognise it as a parasite, if the 

 circumstances under which it was found had not emphatically settled 

 the point. For the previous feeding, and the encapsulation of the 

 cysts, which in every respect corresponded to a Oz/s^'cemts-bladder, 

 placed the nature of the body beyond a doubt, especially since the 

 appearance and nature of the external envelope, in spite of the in- 

 distinctness of the lamination, recalled in- a very striking way the 

 cuticle of the adult Echinococcus. 



The boundary of the outer wall appeared, as a rule, somewhat 

 sharply defined, but there were some, especially among the larger 

 specimens, in which the border was less distinct, as is also sometimes 

 the case with the zona of mammalian eggs. It was but slightly affected 

 by reagents, as though it already possessed the chemical nature 

 of the later bladder-wall. Its physical nature seemed also identical 

 with that of the later. It was extremely expansible and elastic, so 

 that the diameter of the bladder could be increased by pressure to more 

 than double. No structure could ever be observed in the " zona." 



If left long in water the zona became separated here and there 



1 Naunyn (loc. cit. ) describes in a similar manner the youngest Echinococcus found by 

 him in cattle. " They exhibited," he says, " a bladder of about ,V f a line in diameter, 

 whose wall already showed the structure characteristic of this bladder-worm. It was 

 comparatively thick, and displayed a tolerably distinct concentric lamination. The bladder 

 was tilled with small balls like tubercular granules, or with a fluid in which numerous fat- 

 drops were suspended. The latter appeared, however, to be due to a fatty degeneration 

 that had already set in." 



