3426 



THE WORM-LIKE ANIMALS 



prominent lips. Other mammals, besides man, are the hosts of different species of 

 Ascaris. For instance, A. mystax is found in dogs and cats, and sometimes even in 

 man; while A. lumbricoides also occurs in swine. A large species, A. megalocephalus, 

 the female of which reaches a length of over a foot, lives in 

 horses and cows. A second common parasite of mankind is 

 Oxyuris vermicularis, a small, white, sharp-tailed worm, which 

 measures about one-quarter of an inch in length. It occurs 

 abundantly in children and growing people. As, in the case of 

 Ascaris, it seems that before development can take place, the 

 egg must pass out of the host, and again make its entry into 

 the alimentary canal through the mouth. These worms are 

 so small and light 

 that, when dried, 

 every current of air 

 will scatter them, 

 and they may make 

 their way into the 

 alimentary canal of 

 their host in con- 

 nection with al- 

 most any kind of 

 food. To the fam- 

 ily Strongylidce be- 

 longs a dangerous 



parasite, Dochmius duodenalis, occurring in the intestine. It is 

 about half an inch in length. A peculiarity of this species and 

 others of the genus is that the posterior end of the male is fur- 

 nished with a curious bowl or fan-shaped ruff, which is often 

 supported by thick ribs (a and c of the above figure.) 

 The gullet, at least in individuals that are still growing, is fur- 

 nished with strong teeth (). When this 

 worm appears in masses, it produces the 

 disease known as Egyptian cholera. 



The accompanying illustration is an 

 enlarged view of the head of Cucullanus 

 elegans, a parasite in fresh-water fishes 

 like the perch, and having for its inter- 

 mediate host the Crustacean Cyclops. 

 The worm is about half an inch long, and 

 the aperture of its mouth forms an ellip- 

 tical case with thick brown walls. The 

 female bears living young, which creep 



forth from their egg cases while still within their mother's body, 

 HUMAN THREADWORM, w h ere they may be counted in thousands. Protected by a 



Oxyuris vermicularis 



(much enlarged). tough skin, the worms, which have reached the outside world. 



Dochmius duodenalis. a. Entire ; b. Head (en- 

 larged); c. Tail (enlarged). 



HEAD OF Cucullanus 

 elegans (enlarged). 



