CONTROL OF AM.MAL VAKASITES 



263 



fed the ripe jiro^lottides from 111:111 to calves, ami was thus ahlc to dis- 

 covt'i- how man aoiniircs this tapeworm from eatin^^ measly beef. The 

 tiiiv egg hatches in the stomach of the cow, Imrrows tliroiiL;h the wall 

 of the intestine, and in from tlirce to six months lias grown to a 

 bladder, or cyst (the cysticerctis), tlie size of a small bean, and is then 

 found in the muscles. After the cysticercus passes through the human 

 stomach, the head everts (l)Ops out like turning a glove-finger), bringing 

 the hooks and suckers to the 



outside; these anchor in the Man 



intestine and begin a new life 

 cycle. AVhile the beef tape- 

 worm {I'd Ilia sdf/iiKitd') may 

 cause some irritation, an<l un- 

 doubtedly steals some digested 

 food, it seldom does serious 

 injury. This is due to the 

 simple fact that its eggs can- 

 not hatch and pass into cysti- 

 cerci in the mnscles or other 

 organs of man. The cysticer- 

 cus stage is confined closely to 

 cattle, and the adult stage as 

 closely to man. The eggs of sev- 

 eral of the other species do, how- 

 ever, develop cysticerci in man, 

 which renders them much more 

 dangerous and sometimes fatal. 



The pig tapeworm — Tcsnia solium. This jtarasite is distributed the 

 world over, wherever the pig is raised and eaten raw or rare. It is found 

 alscj in the wild boar, sheep, deer, dog, cat, bear, and monkey. The eggs 

 and newly hatched embryos (oncospheres) are microscopic, the latter 

 only 0.02 millimeter in diameter — so small that they are easily carried 

 to foods on dirty hands, eaten with })olluted vegetables, or even swal- 

 lowed by flies and carried to foods anywhere. These eggs, if swallowed, 

 may find their way to any part of the body — muscles, eyes, brain, and 

 even heart, and there become cysticerci. These, too, are large ((j-2() milli- 

 meters long by 5-10 millimeters thick), so that even on»' may prove fatal. 

 In expelling this tai)eworm great care must be used to avoid causing nau- 

 sea, for a single ripe jn-oglottis, forced back into the stomach and releas- 

 ing its myriad embryos, would leave little chance for a [tatient's recovery. 



Hog 

 (cyst ceU\ 



Man 

 (cyst cell\ 



Fi<;. 115. Life cycle of pig tapeworm ; 

 infection from uncooked pork 



