chapter xxiv 

 xe:\iatoda. family vii. trichixellid.e 



Xematoda (p. 217j. 



The nematodes of this faniil}' have a very slender and elongated 

 anterior portion of the body, containing only the esophagus. The pos- 

 terior portion is more or less enlarged and is occupied h)y the intestine 

 and reproductive organs. The mouth is rounded and nude. The anus 

 is terminal or nearly so. The males have a single testis and but one 

 spicule or the spicule may be absent. The females have a single ovary. 

 The vulva is located at the junction of the smaller with the larger por- 

 tion of the bodj'. They are oviparous (Trichuris) or ovoviviparous 

 (Trichinella). 



The worms of this group to be described come under two genera, — 

 Trichuris and Trichinella. Of those but one species, — Trichinella 

 spiralis, is of pathologic importance. 



Trichuris ovis fTrichocephalus affinisj. Fig. IGO. Trichinelhdse 

 (p. 299). — The esophageal portion of the body is very long and slender; 

 the posterior portion, containing the reproductive organs, much thicker. 

 The head is sometimes provided with two transparent wing-like en- 

 largements. The posterior extremity is more or less blunt and rounded. 

 The body is transversely striated. The posterior portion of the body 

 of the male is rolled dorsally in a spiral. The spicule is verj- long, 

 measuring 5-7 mm. (7/32-9/32 of an inch) and terminating in a sharp 

 point. 



The female is 50-70 mm. (2-2 3/4 inches) in length, the esophageal 

 portion constituting about two-thirds of the total length. The male is 

 50-80 mm. (2-3 1/8 inches) in length, the esophageal portion in the 

 same proportion to the total length as in the female. 



The eggs are lemon-.shaped, 70-80 microns long, and have an opercular 

 plug at each end. Development is direct. 



This species is a common para.site in the large intestine of ruminants, 

 particularly the sheep and goat. Leuckart has demonstrated that it 

 develops directly from the egg without intermediate host and without 

 a free hving stage. When the eggs are taken into the intestine of the 

 nmiinant host the embr>'OS are freed and attain their adult development 

 in about sixteen daj's. They are usually found attached firmly to the 

 mucosa, but apparently cause littlo if any trouble. 



Trichuris crenatus ' Trichocephalus crenatus). Trichinellidae (p. 

 299). — The esophageal portion of the body is very slender, the posterior 



