FORMATION OF DAUGHTER-BLADDERS. 611 



as a big hazel-nut. Under some circumstances it is postponed to a 

 still later stage. In a cow which. I examined, where lungs and liver 

 were penetrated with perhaps 150 Echinococci, there were, besides the 

 usual bladders thickly beset with brood-capsules, others which were 

 still barren, although they had attained the size of a hen's egg, while 

 in others, with a diameter of 10 mm., the formation of heads had 

 already begun. In the so-called " Echinococcus multilocularis" the 

 heads were sometimes found in bladders with a diameter of less 

 than 1 mm. 



We do not know how these differences are conditioned, nor how 

 it comes about that certain Echinococci (the acephalocysts) never form 

 brood-capsules or heads at all. One may indeed suppose that the 

 nature of the parenchymal sheath is a determinant factor, but what the 

 special peculiarities are is as yet unknown, and will probably remain 

 unknown for long, owing to the difficulties which beset a thorough 

 histological analysis of the bladder-wall. 1 This is also true in regard 

 to the causes of sterility, 2 though disturbances of nutrition are pro- 

 bably largely influential in this connection. 



The Formation of Daughter -Bladders and the different Forms of 

 the Echinococcus. 



Kuhn, " Recherches sur les Ac6phalocystes : " Strassbourg, 1832. 



Naunyn, " Entwickelung des Echinococcus," Mutter's Archiv f. Anat. u. Pkysiol., 

 p. 612, 1862. 



Rasmussen, "Bidrag til Kundskab om Echinococcernes Udvikling," Vid. Meddel. 

 not. Foren. Kjobenhavn, p. 1, 1865. 



With the above-described changes, the Tcenia echinococcus has 

 completed the bladder-worm stage of its development. The originally 

 very small, six-hooked embryo has grown into a large bladder, which 

 is beset internally with brood-capsules, which again produce an 

 immense number of tape-worm heads. 



What distinguishes the Echinococcus from other bladder- worms is 

 not so much the great number of these heads, as the appearance of 

 special brood-capsules, whose structure and development proves them 

 to be structures as distinct as the bladder and head. They are related 

 to the bladder, as the twigs of a tree are to the stem from which 



1 These difficulties explain the numerous erroneous hypotheses which interpret the 

 parenchyma sheath even as a fat deposit, a simple epithelium, &c. But we need not 

 point out that such views are inconsistent with any appreciation of the physiological 

 importance of this layer, which represents neither more nor less than the whole of the 

 active organic apparatus of the Echinococcus. 



2 Helm, " Ueber die Productivity und Sterilitat der Echinococcusblasen," Archiv f. 

 pathol. Anat., Bd. Ixxix., p. 141, 1880. 



