BEEF TAPEWORM 



239 



Dibothriocephalidse, in which the head is flat and possesses two 

 slitlike suckers (Fig. 87C and D). The latter family also differs 

 from the Tseniidse in having eggs with lids like those of the 

 flukes (Fig. 88A), and without developed embryos when passed 

 in the faeces. 



Family Taeniidae 



Beef Tapeworm. The commonest human tapeworm in most 

 parts of the world is the beef tapeworm, Tcenia saginata. The 

 adult of this species as it occurs in the 

 human small intestine consists of over 

 1000 proglottids, and grows to a length of 

 15 or 20 feet; cases have been reported 

 of specimens of this tapeworm which 

 measured 35 to 40 feet, though in some 

 of these cases there were probably several 

 tapeworms infesting a single person. 

 When two or more worms are expelled 

 in pieces it would naturally be easy to 

 measure them as parts of a single one. 



The scolex of the beef tapeworm (Fig. 

 82 A) is hardly larger than the head of a 

 pin. It possesses four small suckers for 

 adhering to the wall of the intestine, but 

 there is no crown of hooks. The suckers 

 are apparently quite sufficient for main- 

 taining a hold, if one should judge from 

 the difficulty experienced in dislodging the 

 worm from the intestine. 



The proglottids gradually increase in 

 size as they get farther from the scolex (Fig. 81), and the organs 

 contained in them develop slowly. The general form of a sexu- 

 ally mature proglottid and the appearance and arrangements of 

 the organs are shown in Fig. 83. Shortly after sexual maturity has 

 been reached and the sperms for fertilizing the eggs have been 

 received, the uterus begins to grow and develop lateral branches 

 to accommodate the rapidly forming eggs. When fully developed 

 the gravid proglottid enlarges, becoming three or four times as 

 long as when sexually mature, and resembles a pumpkin seed 

 in shape. The greatly developed uterus, distended with eggs, 



FIG. 88. Gravid segment 

 of Tcenia saginata. X 4. 

 (After Stiles.) 



