168 ROUNDWORMS— THE NEMATHELMINTHES 



8. Explain the physiological effects of Trichinella infection. 



9. Trace the life cycle of the pinworm. 



10. Give the physiological cause of elephantiasis. 



11. What popular superstition is associated with the hair worm? 



12. Explain how hogs and people become infected with Trichinella. 



13. Many of those who get ascaris infection also develop pneumonia. Why 

 is this? 



14. Explain how commensalism differs from parasitism. 



15. Why is it said that an ideal parasite does not do much harm to its host? 



16. How can parasitic worms live in the intestine without being digested by 

 the enzymes which are present around them? 



17. In what ways has the tapeworm become so specialized as a parasite that 

 it could not exist as a free-living form ? 



18. Many people are bitten by mosquitoes carrying the sporozoites of bird 

 malaria, yet they do not develop the disease. What is the probable explanation for 

 this? 



