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PLATHELMINTHES 



hooks. These parts are at first inverted and only come to their definitive 

 position on the outside of the scolex when the latter is protruded as one 

 would turn out the finger of a glove. Rarely is the scolex protruded at 

 this time (cysticercus of the mouse liver) and begins the formation of 

 proglottids. Even in this case they do not become sexually mature until 

 in the intestine of the cat. 



The further development follows when the cysticercus is taken into the 

 stomach of the new host When man, for instance, eats infected ('measly') 



FIG. 230. Structure and development of tli2 cysticerus (C. cellulosae of Tcenia 

 solium). a, measly meat, natural size; below an escaped cysticercus; b, cysticercus, 

 with exserted scolex, enlarged; ce, development of the scolex, more enlarged; c, young 

 cysticercus with blastema of scolex (above) and water-vascular net; d, e, different stages 

 of scolex in receptaculum, the cysticercal wall mostly removed. 



pork, the cysticerci are freed by action of the digestive juices and the scolex 

 is everted. The embryo passes to the intestine, becomes attached and, 

 surrounded by nourishment, begins to grow, the bladder remaining at- 

 tached to the hinder end. Soon the formation of proglottids begins in the 

 piece connecting the bladder with the scolex So rapid is the growth that 

 in ten or twelve weeks Tcenia solium begins to set proglottids free. 



In cases where the bladder reaches a considerable size it may produce more 

 than a single scolex. The bladder of Ccenurus cerebralis, which lives in the 

 brain of sheep, produces hundreds of scolices. The number is even greater in 

 Tcenia echinococcus , in which the bladder increases by budding, and by the 



