PSEUDOCOELOMATE AND MINOR EUCOELOMATE PHYLA 



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Fig. 12.5. Class Nematoda. A, adult female trichina worm, Trichinella spiralis: this sta^e 

 inhabits the intestine of the host and produces thousands of juvenile worms which pass into the 

 circulating blood and reach various tissues, chiefly muscles, where they encyst. B, encysted 

 juvenile worm in striated muscle. {A, redrawn from C. G. Goodchild in F. A. Brown, Jr., el 

 a/.. Selected Invertebrate Types, copyright 1950 by John Wiley and Sons, Inc., printed by 

 permission; B, photograph courtesy General Biological Supply House, Inc.) 



of the host and ingest tissue fragments and blood. They are considerably 

 more dangerous to the host than the ascaris, occurring in more massive in- 

 festations and causing serious loss of blood. Certain sections of the United 

 States have undoubtedly been retarded in their development by the prev- 

 alence of hookworm infestations among the rural populations. As a result of 

 active campaigns by public-health authorities and others, the situation has 

 been much improved. 



Other important nematode parasites of humans are the trichina worm, 

 Trichinella spiralis (Fig. 12.5), which lives as an adult in the intestine of man 

 and as encysted juveniles in the muscles of this host and a variety of others, 

 including swine; and the filarial worms, such as Wuchereria bancrofti, which 

 inhabits the lymph glands of man and requires a mosquito as an intermediate 

 host. Details of the life cycles and pathological effects of these and many 

 other interesting nematode parasites will be found in any textbook of 

 parasitology. 



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