FLATWORMS AND THREADWORMS 



297 



the various stages already mentioned and produces considerable anaemia. 

 The genital openings are on the face of each segment in Bothriocephalus 

 latus instead of at the edges as in Taenia. 



Taenia echinococcus differs from the three forms just mentioned in 

 that man is the intermediate host and the dog the true host 



It also differs in size from those mentioned. Tapeworms in the 

 human being may reach a length of thirty to forty feet, but Taenia 

 echinococcus is only three mm. to six mm. in length. In cold countries 

 where men and dogs live in the same room and where dogs lick their 

 master's faces, eggs are transmitted to. the human digestive tract, al- 

 though intermediate hosts other than man are possible. 



The developing cyst in the instance of the small worm is very large, 

 and there is a closely allied form known as Taenia multilocularis which 

 cften is present with Taenia echinococcus, and when this is the case, a 

 great mass of ramifying spongy tissue, full of small cavities, forms. If 

 these cysts grow in the brain the sheer pressure of the cysts cause injury 

 and then, too, if the first cyst ruptures it pours out poisons in the sys- 

 tem, as well as again spreading new larvae which form secondary cysts. 



The eggs, when in the human intestine, hatch and bore through the 

 intestinal wall and are swept along by the blood-stream to their lodging 

 place. A thin, pearl-colored covering then surrounds it and about this 

 the tissues of the host react so as to form a capsule. A liquid is formed 

 in the thin membrane while buds grow out of the membrane. These 

 buds are finally recognizable as the heads of new worms. The heads 

 turn inside out, causing the hooks to face inward. This makes it possi- 

 ble for the worm to be swallowed by dogs and pigs. Then the head 

 turns back again to make use of its hooks and suckers. If no interme- 

 diate host is found, the worms may die, but in such a case there is a 

 large cyst filled with a mortar-like white material remaining. 



Following is a summary of all the important 

 Tapeworms and their hosts: 



Name 

 Taenia solium . 



Taenia saginata 



Final Host 



Man 



Man 



Taenia elliptica 



Taenia cucumerina 



(Both of these are also! 

 called 

 Dipylidium caninum . . . . | 



Taenia flavo-punctata . . . 



cat mostly, 

 but also man . 



Common in rats. . 



Intermediate Host 

 Hog (in liver, mus- 

 cles, brain and 

 eye). 



Ox and Giraffe (in 

 muscles). 



In body-cavity of 

 dog, fleas and lice. 



Moths and beetles. 



