298 



General Biology 



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, 

 although 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 

 often 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 into the sys- 

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



The egg, when in the human intestine, hatches and bores through 

 the intesinal wall and is swept along by the blood-stream to its 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 possible 

 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 intermediate 

 host is found, the worms may die, but in such a case a large cyst filled 

 with a mortar-like white material remains. Following is a summary 

 of all the important tapeworms and their hosts : 



Name 

 Taenia solium . 



Taenia saginata 



Taenia elliptica 



Taenia cucumerina 



(Both of these are also 

 called 

 Dipylidium caninum 



Taenia flavo-punctata .... 

 (Hymenolepsis diminuta) 



Taenia nana 



(Hymenolepsis nana) .... 



Taenia confusa 



Final Host 



Man 



Man 



Dog and cat mostly 

 but also man 



Common in rats 



Twelve cases known 



in man. 

 Common in Italy 



and known in 



America. 



A few cases in Man. 



Intermediate Host 

 Hog (in liver, mus- 

 cles, brain, and 

 eye). 

 Ox and giraffe (in 

 muscles). 



I n body - cavity o f 

 dog, fleas and lice. 



Moths and beetles. 



