148 



FIRST LESSONS IN ZOOLOGY 



The IbrmiiiL;" rif these thousands of tin}' cysts injures the 

 muscles and causes great pain, sometimes death to the 

 host. Such infested muscle or flesh is said to be " trichi- 

 nosed," and the flesh of a trichinosed human subject has 

 been estimated to contain 100,000,000 encysted worms. 

 To complete the development of the encysted and sexless 

 Trichinre the infested flesh of the host must be eaten b}- 

 another animal in which the worm can live, e.g., the flesh 

 of man b)' a pig or rat, and that of a pig by man. In 



Fk;. 1 10.— Tapeworm; head magnified, at left; wliole worm may be 

 beveral yards long. (After Leuekart.) 



such a case the cysts being dissolved by the digestive 

 juices, the worms escape, develop reproductive organs 

 and produce young, which then migrate into the muscles 

 and induce trichinosis as before. But, however badly 

 trichinosed a piece of pork may be, thorough cooking of 

 it will kill the encysted trichina;, so that it ma}' be eaten 

 without danger. Some people, however, arc accustomed 

 to eat ham, which is simpl}- smoked pork, A\ithout cook- 

 ing it, and in such cases there is al\\'a}-s great danger. 



