DEATH OF THE BLADDER-WORM. 385 



ever forming themselves anew. It is probable that the ordinary 

 bladder-worms do not usually persist in their hosts more than a few 

 years. 



In the examination of measly animals one sometimes finds 

 specimens with protruded head, which have a very turbid, withered 

 appearance, and exhibit no signs of life. When the surrounding cyst 

 is unmodified, one may plausibly conclude that the parasites have 

 died a natural death. As a rule, however, the cause of death must 

 be sought in the pathological state and modification of the surround- 

 ing connective-tissue capsule. In such cases the secretory activity of 

 the capsule has probably been in some way altered. Indeed one 

 sometimes finds not only cysts whose under surface has an abnormal 

 character — perhaps strongly injected or covered with small prolifera- 

 tions — but also others which have a bloody or even purulent fluid 

 next the worm. 



When the worm dies, whether from internal or external causes, 

 its body-parenchyma at once begins to get turbid, and its bladder-fluid 

 to be absorbed. The latter is gradually thickened, and acquires an 

 ahnost gummy character. Afterwards the worm undergoes the same 

 changes as may be observed in foreign substances introduced into 

 the body-cavity. As the body of the worm becomes more and more 

 shrivelled up and deformed, the albuminoids become displaced by a 

 fatty mass which fills the collapsed connective-tissue cyst, and is 

 finally calcified by the deposition of lime salts in varying abundance. 

 On closer examination one often finds inside such cysts the still un- 

 changed tape-worm hooks, which most indisputably prove the origin 

 and nature of the apparent pseudoplasms. 



In some cases these changes undergone by the dead bladder-worm 

 exhibit various, but little studied, divergences. Thus there is in the 

 pathological collection at Giessen a Cysticercus tenuicoUis whose caudal 

 bladder — not the cyst, as one might sooner have expected — is calcified 

 all over, and seems almost ossified, without the form being at all 

 altered. 



Having now discussed the development of the tape-worms in its 

 most important modifications, let us cast a glance at their Ufe- 

 history. Five successive stages are to be noted : (1.) the six-hooked 

 embryo; (2.) the bladder-worm or Cysticercus; (3.) the tape-worm 

 head without joints (Scolex) ; (4.) the proper chain -like worm (Strobila) ; 

 and (5.) finally, the isolated sexual animal or Proglottis. The life- 

 history of the Cestodes is therefore much richer and more complicated 

 than we usually find even among the lower animals. 



On closer examination these five phases are reduced to three 

 different forms,— the ©/pffief^fiS^ri^Cf^flli^e-worm head, and the 



2 B 



