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GENERAL BIOLOGY 



Fig. 183. Tapeworms. 



A. The Life-History of Tcenia solium. 1, six-hooked embryo in egg-case; 2, 

 proscolex or bladder-worm stage, with invaginated head ; 3, bladder-worm with 

 evaginated head ; 4, enlarged head of adult, showing suckers and hooks ; 5, general 

 view of the tapeworm, from small head and thin neck to the ripe joints ; 6, a ripe 

 joint or proglottis with branched uterus ; all other organs are now lost. 



B. A proglottis of Toenia solium with the reproductive organs at the stage 

 of complete development, cs., Cirrus sac ; excr., excretory canals ; g.o., genital 

 opening ; n.c., nerve cord ; ov., ovary ; sh.g., shell gland ; t., testes ; v.d., vas 

 deferens ; ut., uterus ; vat]., vagina ; y-g., yolk gland. 



C. Diagrams of Bladder-Worms. I. The ordinary Cysticercus type, with one . ,. 

 head. II. The Coenurus type, with many heads. IIL The Echinococcus type, with 

 many heads, and with blood capsules producing many heads. 



D. Portion of hog's liver infested with echinococcus bladder-worm. A, after 

 Leuckart; B and C, after Borradaile ; D, after Stiles.) 



then come in contact with grass, weeds, hay, or any vegetation which 

 cattle eat, they hatch in the intestine of the animal eating such vegeta- 

 tion. Each egg will develop a little six-hooked embryo which leaves the 

 egg and bores its way into the cow's body. It comes to rest either in 

 the liver or muscle tissue. 



In about three months a bladder-worm known as a cysticercus has 

 developed, and if flesh containing these bladder worms is eaten by man, 

 he is in turn infected. 



The cysticercus is really a tiny bladder-like sac with a scolex pushed 

 in on one side. When this gets into man's intestine, the scolex is pushed 



