266 GENERAL ZOOLOGY 



and pass out with the undigested portion of the person's 

 food. Sometimes the embryos, inclosed in their thick mem- 

 branes, are swallowed by cattle while drinking at pools. In 

 the intestine of the cattle the membrane of the embryo is dis- 

 solved, and the freed larva bores its way through the wall of 

 the intestine, and finally comes to rest in the muscular tissue. 

 It remains there until the muscle is consumed by man. If 

 the larva has not been killed by cooking, it develops in man's 

 intestine into the mature tapeworm. 



Other Tapeworms of Man. Another species of tapeworm 

 (Tse'nia so' Hum) found in human beings comes from un- 

 cooked pork. Tapeworms are not necessarily fatal. The 

 annoyance is considerable, however, until, by a period of 

 fasting and medical treatment, the head of the parasite is 

 removed from the intestine. The fish tapeworm of man is of 

 restricted distribution, for it occurs in only a few localities 

 near lakes where the inhabitants eat raw fish containing the 

 living larva?. 



Prevention. Government inspection of meat in the pack- 

 ing houses has been an important agency in reducing the 

 numbers of cases of beef tapeworm and pork tapeworm in 

 man, for these worms get into the human body only when 

 raw or partially cooked beef or pork containing living larva? 

 is eaten. Government inspectors examine the hogs and 

 cattle in the packing houses which are under federal in- 

 spection, and if larval tapeworms are found the animal is 

 not sold for meat. 



The class to which the tapeworms belong is called 

 Cesto'da (Gr. kestos, " girdle"; eidos, "form"). 



Definition of Plathelminthes (Gr. platys, "flat"; helmins, 

 "worm"). The members of the phylum Plathelmin'thes 

 are worms with flattened bodies that are not divided into 

 somites. Almost all the species are hermaphroditic. All 

 the flatworms lack a body cavity. 



