LARVAL TAPEWORMS IN MAN 247 



attaching itself to the wall of the small intestine, begins to grow 

 into an adult worm at the rate of about 31 to 32 proglottids a 

 day. The mature eggs begin to appear in the faeces within a 

 month. 



The fish tapeworm is especially active in the production of 

 toxins which cause intense anemia. Its head has been found 

 to produce oleic acid, a substance which has blood-destroying 

 properties. Often the nervous symptoms produced by this 

 species are also very marked. 



Two other species of Dibothriocephalidse have been found in 

 man. One of these, Dibothriocephalus cordatus (Figs. 84G and 

 87D), occurs in dogs, seals and other fish-eating animals in Green- 

 land. It only accidentally establishes itself in man. Diplo- 

 gonoporus grandis is a very large species, found in Japan, in 

 which there is a double set of reproductive organs. The genital 

 openings are arranged in two longitudinal grooves on the ventral 

 side of the worm (Fig. 84F). This species is rare in man. 



Larval Tapeworms in Man 



There are several species of tapeworms which inhabit the human 

 body in the larval or bladderworm stage. Three types are found 

 in man. Most important are the huge multiple cysts or "hyda- 

 tids " of Echinococcus granulosus, a small tapeworm of dogs. 

 Second, there are the bladder worms of the common pork tape- 

 worm, Tcenia solium, which often occur in large numbers, and 

 may be of very serious nature if located in important organs. 

 And, finally, there are two species of Sparganum. This is not 

 a true genus but is a collective group of larval tapeworms of the 

 plerocercoid type which cannot be definitely classified because 

 the adult is unknown. 



Echinococcus hydatids. In some parts of the world infection 

 with the hydatids or larvae of Echinococcus is very common, 

 especially in children. In Iceland, where there is very close asso- 

 ciation between the human and the canine population, two or 

 three per cent of the inhabitants are afflicted, and in certain dis- 

 tricts as high as ten per cent. In Australia, also, this tapeworm 

 is common in dogs and its larvae occur in a considerable pro- 

 portion of human beings as well as in stock. In the United 

 States, especially in the southeastern states, it is fairly common, 



