382 ARTICULATA : WORMS. 



SUB-SECTION VIII. 

 THE ORDER OF CESTOIDEA, OR TAPE-WORMS. 



THE name Cestoidea comes from the Greek kestos, a 

 girdle. The Cestoids are flat, tape-like worms, and 

 narrow towards the head, but widening behind; in their 

 mature state they live only in the intestines of vertebrate 

 animals. They vary from a few inches to many feet in 

 length. The largest attain, in some cases, the length of 

 one hundred feet. The width is nearly an inch in 

 some of the widest. 



The eggs of a cestoid never hatch in the same intestine 

 in which the cestoid lives, but only after they have been 

 taken into the stomach of another and suitable animal. 

 Thence the embryos pierce their way into the blood- 

 vessels, and are carried by the circulation of the blood 

 into various parts of the body, where they develop into 

 larvse called hydaMds. 



The so-called " measly pork " is pork containing these 

 hydatids ; that is, measly hogs are such as have their 

 flesh more or less filled with the larvae of cestoids or tape- 

 worms. And if the flesh of such hogs be eaten before 

 cooking, which kills the hydatids, the man or animal 

 eating it takes these hydatids into his intestines, where 

 they develop into tape-worms. 



And so in regard to all animals which have tape- 

 worms ; they get them by eating other animals in whose 

 tissues there exist hydatids. And the way in which 

 those animals afflicted with the hydatids get the latter, is 

 by swallowing some of the infinitesimal eggs of the tape- 

 worm. 



