302 GENERAL BIOLOGY 



difference, the space between intestinal tract and body wall is called a 

 coelom in worms. 



Nematode Infections (Figs. 185, 186, 187, 188). 



Ascaris lumbricoides is found chiefly in children. The female is 

 from seven to twelve inches in length and the male from four to eight 

 inches. The worm is pointed at both ends and of a yellowish-brown or 

 slightly reddish color. There is no intermediate host. The animal oc- 

 cupies the upper portion of the small intestine. Usually one or two are 

 found in a single location, although sometimes vast numbers of them 

 may be found. The worm may pass to the stomach and be vomited 

 forth, or -it may crawl up the oesophagus and then pass into the larynx 

 and asphyxiate the patient. In fact, it may enter any ducts or tubes 

 in the body. 



Oxyuris vermicularis (commonly called pin-worms 

 or thread- worms), (Fig. 188), are parasites of the rec- 

 tum and colon. The male is about 4 mm. long and 

 the female about 10 mm. The parasites migrate and 

 come close to the surface during the night, thus caus- 

 ing accentuated irritation and itching about the rec- 

 tum and genital organs. Many eggs are found in the 

 faeces of infected children. It is essential that the dis- 

 tinguishing and diagnostic difference between oxyuris 

 The Hookworm. eggs and trichocephalus eggs be known. Both tvpes 



a., male; &., fe- . 1M 1-1 , i 



male; o., mouth; v., are quite alike except that trichocephalus eggs have a 

 o P f en e n g g g f s OT dis f A a f r tS button-like lighter area (Fig. 189, 16). Re-infection 

 must be guarded against. These worms often find their 

 way into the appendix of children where they drill into the mucous mem- 

 brane and cause appendicitis. Trichina (Fig. 187), (also called Trichi- 

 nella spiralis), lives in the small intestine when adult. The disease 

 trichiniasis is caused by the embryos after they pass from the intestines 

 to the voluntary muscles where they encapsulate themselves as larvae. 



The female is 3 to 4 mm. long and the male 1.5 mm. There are two 

 tiny projections from the posterior end of the worm. The larvae, when 

 encased in the muscle, is about 1 mm. long. Trichina have a pointed 

 head and a somewhat rounded tail. The parasites are ingested by man 

 when eating inadequately cooked pork. Each worm may produce as 

 high as 10,000 young, which are either placed directly into the lymphatics 

 by the female or burrow through the intestinal wall. They then encyst 

 in the muscle tissue. Pigs acquire the disease by eating offal or infected 

 rats. 



Twenty-six different kinds of animals have been found in which 

 trichinae grow, and as many as 15,000 of these parasites have been found 

 in one gram of muscle. 



