210 PARASITES IN THE INTESTINES 



requiring three to four months to produce embryos, which, 

 when introduced into the digestive tract, attain complete 

 development in two to three months. The trichuris does 

 not require an intermediate host; embryonic development 

 takes place entirely outside the body and the parasite 

 must pass into the digestive canal while still enveloped in 

 its shell. This species is often found in animals affected with 

 severe anemia, but it does not appear to play other than a 

 secondary part in the development of the disease. When 

 present in considerable numbers in the cecum, however, it 

 may cause a chronic inflammatory condition by its repeated 

 injuries to the mucosa. 



The ova differ considerably from those of other intestinal 

 parasites, being ovoid, 70 to 80 microns long and 30 to 35 

 microns broad, of a distinct yellow color, and have at each 

 end a small rounded projection which appears clear under the 

 microscope. 



Birds are occasionally infested but the parasite is rarely 

 present in large numbers, and the anemia it produces is only 

 secondary to the chronic enteritis which results. 



Trichinellidae in the Intestine of the Dog. — Trichuris 

 depressiusculus.— This species is often spoken of as the 

 whipworm, owing to the resemblance of the body to a whip. 

 It is 45 to 75 mm. long. The anterior half of the body is 

 much smaller than the posterior part and the tail is usually 

 curved. 



Trichinellide in the Intestine of the Rabbit.— Trichuris 

 unguiculatus.— This species is rare and is only occasionally 

 found in the large intestine and cecum of the wild rabbit 

 and the hare. The male is 3 to 4 cm., the female 3 to 

 5 cm. long. 



Trichinellide in the Intestine of Birds. — (a) Trichosomum 

 retusum.— Male 13 mm., female 19 mm. long. Body white 

 or yellowish-white, tail blunt. 



(b) Trichosomum annulatum.—'Male 15 mm., female 80 

 mm. long. Body white and very attenuated at its anterior 

 extremity and marked with close annular stripes. 



(c) Trichosomum collare.— Male 8 to 10 mm., female 9 to 

 12 mm. long. 



