434 



THE ANIMAL PARASITES OF MAN 



Genus. Trichostrongylus, Looss, 1905. 



Very small Strongylidce. Mouth with three small lips and nodular 

 or punctiform papillae. Cervical papillae absent. Bursa entirely 

 closed, with large lateral lobes, and median lobe not distinctly defined. 

 Anterior 1 rays double, the branches widely divergent, one thin, 

 the other thick, and close to the antero-median. The postero- 

 median ray is thin and close to the postero-external. Posterior ray 

 bifurcate, each branch bifid at the tip (fig. 311). Spicules short, spoon 

 or spatula-like, with on the broad anterior end a lateral knob or disc 

 and in front of the point an angular projection. Gubernaculum of a 

 peculiar canoe or shoe shape in profile. Vulva in the hinder half of 

 the body. Tail with two minute papillae just in front of tip. Eggs 

 thin shelled ; when laid they show eight to thirty-two segments. 

 Parasitic in duodenum, seldom in the stomach of herbivora. 



Trichostrongylus instabilis, 2 Railliet, 1893. 



Syn. : Strongylus instabilis, Railliet, 1893; Strongylus subtilis, Looss, 1895. 



Male 4 to 5*5 mm. long, cro8 mm. thick in front of bursa. 

 Spicule 0*135 to o'i45 mm. long, accessory piece (gubernaculum) 

 0*07 mm. thick. Antero-external ray usually thickest of all, occa- 

 sionally only as thick as the 

 antero-median ; postero-median 

 far more slender than the antero- 

 external and antero-median and 



FIG. 309. Trichostrongyhis instabilis ; left, 



posterior end of male ; right, spicule and FIG. 310. Trichostrongylus instabilis .- 



gubernaculum, side view. Cf. fig. 311. Mag- posterior end of female. Magnified, 



nified. (After Looss.) (After Looss.) 



nearer to the postero-external than to the antero-median. Female 

 5 to 6 mm. long, vulva 1-05 to i'2 mm. distant from the tip of the 



1 When the anterior ray is double, the branches of it are called antero -anterior and latero- 

 anterior. 



2 Identical with T. cohibriformis of the sheep according to Leiper. If so, this latter name 

 has priority. 



