. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 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 Tseniidae Beef Tapeworm. — The commonest human tapeworm in most parts of the world is the beef tapeworm, Taenia saginata. The adult of this species as it occurs in the human small intestine consists of over 1000 pr
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 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 Tseniidae Beef Tapeworm. — The commonest human tapeworm in most parts of the world is the beef tapeworm, Taenia 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. 82A) 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 suSicient 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 fuUy 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
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