A PERSISTENT PARASITE 341 



substance one or more limpid bladders from the size 

 of a pea to that of a hen's egg." 



' ' And these horrid worms in the bladder, ' ' queried 

 Jules, "no doubt destroy the brain matter, little by 

 little." 



6 i They grow at the expense of the brain. ' 9 



"I can well believe then, that the sheep is unable 

 to stand." 



"Each of these little bladders is a taenia in its first 

 stage of development, and comes from the germ 

 sown by the severed link or joint that the dog ejects 

 with its excrement. As indisputable proof of this, 

 if lambs are made to swallow some of the taenia links 

 ejected by the dog, these lambs soon show themselves 

 to be seized with the staggers, and in their brains 

 are found the bladder-like organisms that cause the 

 disease. The germs contained in the severed pieces 

 of the taenia must therefore hatch in the lamb's in- 

 testines, and the worms thus brought into being must 

 make their way, through a thousand obstacles, to the 

 animal's brain, the only part of its body adapted 

 to the development of the parasite." 



' ' Then it is in the brain that the little worms grow 

 and become bladders as large as hens ' eggs ! ' ' 



" It is only there that they can flourish. But these 

 bladder-shaped worms are only incomplete beings, 

 comparable to the larvae of insects; and as long as 

 they remain in the sheep 's brain their final develop- 

 ment will not be attained. To acquire their final 

 form, to become taenias, tape-worms, these larvae 

 must pass into the dog r s intestines. A conclusive 



