254 



PLATHELMINTHES 



(fig. 225). Immature and mature stages in fishes. Tetrarhymchus* Ryncho- 

 bothrium* Family 4. TETRAPHYLLID.*:. Head with four very mobile suckers 

 often armed with hooks. Echinobothrium* Acanthobothrium* 



Family 5 BOTHEIOCEPHALID^. Scolex and proglottids present; head 



spatulate, with two sucking grooves on the 

 narrower sides. Bothriocephalus latus* (fig. 

 234), the largest tapeworm in the human intes- 

 tine (also dogs and cats), may reach a length 

 of forty feet and consist of over four thousand 

 proglottids. As said above, the pleurocercoid 

 occurs in fishes, and man acquires the parasite 

 by eating uncooked fish. It is abundant in 

 Russia, Prussia, and Switzerland; rare in 

 America. 



Family 6. TJENIADJE. With scolex and 

 separable proglottids; the scolex always bears 

 four suckers and in many a rostellum with a 

 circle of hooks (fig. 234). In the proglottids 

 the genital pore occurs usually laterally in the 

 proglottids, alternating right and left, rarely 

 only on one side. It is rarely doubled in a 

 proglottid. Intermediate stage a cysticercus or 

 cysticercoid. The human tapeworms are here 

 subdivided accordingly as the sexual animal or 

 the cysticercus has been found in man. 



A Tccnia sexually mature in the human 

 intestine. Most noticeable are Tccnia sol him* 

 and T. saginata* the differences between which 

 are shown in fig. 234. In spite of the lack of 

 hooks, the stronger suckers render T. saginata 

 more difficult to expel. Tccnia solium is not 

 rare in the 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 possibly 

 occur through internal infection; pieces of the 

 worm passing the pylorus and entering the 

 stomach, where they are digested, setting the 

 233.Caryophyllteus embryos free. 



Many other Tanicc, which are common to 

 other mammals, occur occasionally in the 

 human intestine. In mice and rats occur T. 

 (Hymenolepis) nana* and T. diminuta. The 

 first has recently been very abundant in human 

 intestines in Italy and is probably common with 

 us (fig 112). The worm, an inch or two long, 



FIG. 



mutabilis (after M. 'Schultze). 

 df, vas deferens; civ, vitelline 

 duct; k, scolex; ov, ovaries; ps, 

 penis; i<s, vagina with recepta- 

 rulum se minis; t, testes; ut, 

 uterus; vi, vitellarium; vs, vesi- 

 cula seminalis. 



The connection 



of vagina with the crossing point - <-> >- ~ ^ 



of genital duct, vitelline duct, mav occur in thousands and cause severe injury 

 and uterus is lacking in the figure. This species may develop without an interme- 

 diate host; the eggs taken into the stomach pass 



the cysticercoid stage in its walls and then pass to the intestine to become 

 adult. T. diminuta* which has insects for its intermediate host, has been 

 described from man. 



B. Forms passing the cysticercus stage in man. Besides the cysticercus 



