260 



FLAT WORMS 



of man and a single egg be ingested, we may have hundreds of Taenia larvae produced. 

 The six-hooked embryo, leaving its shell, bores its way through the walls of the 

 alimentary tract and especially seeks the liver, just as the embryo of T. solium seeks 

 the brain and eye. 



Griffith notes that in Australia from 10 to 15% of hydatid cysts 

 occur in the lungs. The cyst wall is quite thin and the hydatid cachexia 

 seems to appear earlier in the lung than in the liver cases. 



In the development of the cyst, after the embryo has come to rest at some point 

 in the liver, we have formed at first an indistinctly laminated external envelope 



s. 



FIG. 70. Tape-worms, i, 2, and 3, Head, melon-shaped segments and egg 

 packet of Dipylidium caninum; 4, 5, 6 and 10, entire worm magnified, head, larval 

 stage in intestinal villus and ovum of Hymenolepis nana; 7, echinococcus cyst; A, 

 mother cyst; D, daughter cyst; E, granddaughter cyst; C, scolex in brood capsule; 

 B, brood capsule; G, parenchymatous layer; F, laminated layer; 8 and 9, Taenia 

 echinococcus; 9, natural size. 



with coarsely granular fluid contents. Later on the contents become transparent, 

 and two distinct layers can be observed: i. The external, markedly laminated one, 

 and 2. the internal one, made up of small cells externally and large cells and cal- 

 careous corpuscles internally. This internal lining membrane is known as the paren- 

 chymatous or germinal layer. When the external layer is incised it curls up by 

 reason of its elasticity. This is characteristic of such a cyst. In addition, we have 

 an enveloping connective-tissue capsule formed by the surrounding liver substance. 

 From the germinal layer arise the brood capsules and the scolices. In these brood 



