252 



THE TAPEWORMS 



The most common type of such tapeworm larvae is Sparganum 

 mansoni (Fig. 98), an elastic worm three to 14 inches in length. 

 It is not segmented, but appears so since it is 

 transversely wrinkled; there is an invaginated 

 scolex at the broader end. These parasites are 

 found coiled in the connective tissue of man 

 and other animals, often causing tumors. The 

 majority of human cases have occurred in Japan, 

 but cases are recorded from many other parts 

 of the world also, including Texas. 



Recently it has been shown that this worm 

 is the larva of Diphyllobothrium mansoni of dogs 

 and cats, which has a life history similar to that 

 of D. latus. The first larva, or procercoid, 

 develops in Cyclops leuckarti, but not in related 

 copepods. The plerocercoid or sparganum stage 

 develops in a large number of different animals, 

 including man, but probably the normal second 

 intermediate hosts are cold-blooded vertebrates, 

 especially frogs and snakes, in which they are 

 very common. When these animals are eaten 

 by dogs or cats the parasite completes its de- 

 velopment to the adult form. 



Another type of Sparganum, which has been 

 termed S. proliferum, was discovered by a 

 Japanese investigator, Ijima, in a Japanese 

 woman in 1904. The skin on a large part of 

 FIG. 98. Spar- her body was much swollen and presented 

 ganum mansoni; nume rous hard pimples. Examination showed 



nat. size. (After . 



Ijima and Mur- thousands of worms which were identified as 

 larval tapeworms of the Sparganum type, 

 imbedded in little oval capsules varying in size from less 

 than one mm. (fa of an inch) in length to six or eight 

 mm. (J of an inch). Young slender worms not yet encysted were 

 also found. In 1907 a similar case occurred in a fisherman in 

 Florida, and the parasites were believed by Dr. Stiles to be either 

 identical with or closely related to the Japanese worm. Two 



