Flat worms and Threadworms 



295 



Fig. 183. Tapeworms. 



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

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

 eyaginated 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 Taenia 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; vag., 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. III. 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.) 



a little six-hooked embryo which leaves the egg and bores its way into 

 the hog's body. It comes to rest either in the liver or muscle tissue. 



In about three months a bladder-w r orm 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 

 outward so that it can fasten its hooks into its new host's intestine. It 

 is now ready to bud off proglottids again. 



At least one per cent of all cattle slaughtered in this country have 



