78 



THE WORM GROUP 



m 



■ ■■ 



esMIh M?^ va a ■■■■ 



'•' . 1§ v i\*f '^^f if) , 



Figure 77. — Trichi- 



NELLA. 



cysts are dissolved by the digestive 

 fluids and the worms are freed. 



These worms then develop eggs and 

 sperms which after uniting mature into 

 young worms and migrate through the 

 intestine into the muscles. The activity 

 of the worms at this stage causes a seri- 

 ous inflammation of the tissues and a 

 disease known as trichinosis (trik-in- 

 o'sis), which is often fatal. Hogs con- 

 tract trichinosis by eating refuse that 

 contains the encysted worms. 



Government inspectors examine pork 

 which is to be exported or sold in large 



quantities to see that it is free from these parasites. The 



smaller sales of pork by local dealers are not inspected 



and the only way to be sure of the harmlessness of the 



meat is to cook it thoroughly. 



Hair Worm. — The only importance that can be attached 



to these worms is the myth about their origin. In almost 



every school will be found 



students who believe that 



horse hairs placed in water 



will develop into " hair 



snakes." It would be a 



pity if a student still be- 

 lieved this after a course in 



biology. 



Let us see how such a 



belief can originate and 



often be thought to be 



proved. The hair snakes 



live for a time in water 



and often in the watering Figure 78. — A Common Tapeworm. 



