CLASS XKMATHKLMINTHES. 27 



elongating by the interposition of new joints next the 

 "head." The older terminal joints are in the meantime 

 falling off. Each of these can move about, and contains 

 a multitude of eggs, which escape to the outer world. 

 The omnivorous hog, perchance, devours some of these 

 eggs ; in its stomach, they hatch, and the young worms 

 distribute themselves through their host, become encysted, 

 and we have what is called "measly pork." These cysts, 

 on opening in the alimentary tract of the animal which 

 has eaten, infected meat, give birth to small Tape-worms, 

 which at once attach themselves to their new host. 



CLASS NEMATHELMINTHES (nem at el min'thez). 



If cider vinegar be closely examined with a hand lens, 

 it will be found to contain a myriad of small active 

 worms, popularly called Vinegar Eels. A description of 

 the anatomy of one of these will epitomize that of the 

 class. 



ORDER NEMATODA (nem a to'da). 



The body of the Vinegar Eel is round and filiform 

 (fil'i form) ; the alimentary canal extends as a tube, from 



FIG. 3". 



Lep tod'e ra ox oph'i la. Vinegar Eel. (Greatly magnified.1 



the anteriorly placed mouth for nearly the entire length 

 of the body; on each side, can often be distinguished a 

 multitude o'f eggs. Though many members of this class 

 live, like the Vinegar Eel, a free life, others are para- 

 sitic. 



The Trichina ctri ki'na) is by far the most dreaded of 

 human parasites. By eating raw or poorly cooked pork, 



