III. CESTODA. 



287 



Family 5. BOTHRIOCEPHALID.E Scolex and proglottids present; head 

 spatulate with two sucking groves on the narrower sides. Most interesting 

 is Bothriocephalus latus (fig. 251), the largest tapeworm which occurs in 

 the human intestine (also dogs and cats), and which may reach a length of 

 forty feet and consist of over four thousand proglottids. As has been out- 

 lined above, the pleurocercoid occurs in fishes, and man acquires the parasite 

 by eating uncooked fish. It is especially abundant in Russia, the eastern 

 provinces of Prussia, and in Switzerland. It is rare in America and occurs 

 most frequently in immigrants. Other species occur in man in Greenland 

 (R cordatus) and China (B. mansoni). 



FIG. 251. Head and ripe proglottids of Bothriocephnlus Intus, the head showing the 

 sucker at the angle, the proglottids the marking produced by the uterus. 



Family 6. T.ENIAD.E. With scolex and separable proglottids; thescolex 

 always bears four suckers and in many a ro- 

 stellum with a circle of hooks (fig. 252). In 

 the proglottids the vitellarium is replaced by 

 an albumen gland; the uterus is caecal, and the 

 genital pore occurs usually laterally in the 

 proglottids, alternating right and left, rarely 

 only on one side (Hymenolepis, Anoplocepha- 

 lus). It is rarely doubled in a proglottid 

 (Dipylidium, Moniezia). Intermediate stage a 

 cysticercus or cysticercoid. The human tape- 

 worms are grouped here together, but are sub- 

 divided accordingly as the sexual animal or 

 the cysticercus has been found in man. 



A. Tcenice sexually mature in the human 

 intestine. Most noticeable are Tcenia solium 

 and T. saginata, the differences between 

 which are shown in fig. 252 and the follow- 

 ing table. It is to be noticed that, in spite of 

 the lack of hooks, the stronger suckers render 

 T. saginata more difficult to expel. Tcenia FIG. 252. Head and ripe pro- 

 solium, as the table shows, is not rare in the f ^ ?' ioiiunT S " ff " 1 " 

 cysticercus stage in man and occurs sometimes in places, like the brain 

 and eyes, where it causes severe injury. These cases are in part explained 

 by lack of cleanliness in the food, which may contain eggs, but it is possible 

 through internal infection ; pieces of the worm passing the pylorus and 

 entering the stomach, where they are digested, setting the embryos free. 



