DIVISION BURS AT A 659 



duced into the mouth or nose by self-infection, fruits, vegetables, 

 etc., hatch, and grow in the small intestine into male and females. 



After fertilization the males die off and the females travel into 

 the cfficum, and later into the colon, and have a great tendency to 



Fig. 287. — Development of Oxyuris vermicularis 

 (After Leuckart, from Stiles.) 



wander through the anus to the outside. The duration of life of 

 0. vermicularis in the human body is not known. 



Pathogenicity. — -In large numbers may set up enterocolitis; in 

 small numbers it causes only irritation. 



DIVISION BURSATA. 



Definition. — Nematoda with true cuticular bursa in the male. 

 Classification. — Leiper gives the following table for the difierentia- 

 tion of the various bursate families represented by species in man : — 



A. Mouth with simple pore; no buccal capsule: — 



(a) Male with large bursa and elongated rays; female 

 oviparous, uteri divergent, ovij ect or s present. Intes- 

 tinal parasites — TrichostrongyUdcB. 



(6) Male with short bursa and stunted rays; female ovip- 

 arous, uteri convergent, ovij ect ors absent. Lung 

 par asit es —Metastrongylidce . 



B. Mouth a simple opening, leading into a large buccal capsule 



guarded by chitinous structures: — 

 [a] Mouth capsule bent dorsally and guarded by paired 

 bilaterally arranged plates- — AncylostomidcB. 

 Plates with smooth edge — Necator. 

 Plates with toothed edge—Ancylostoma. 

 (h) Mouth capsule terminal guarded by ring of setae — 

 StrongylidcB. 



BURSATA. 



Family ii. Strongylid^ Cobbold, 1864. 



Nematoda with cylindroid, rarety filiform bodies, mouth usually 

 with wide buccal capsule, with ring of chitinous armature, and an 

 oesophagus more or less enlarged posteriorly. Male with a bursa 

 copulatrix and two equal spicules. Female with two ovaries; 

 vulva situated medialty or posteriorly. As a rule, the species are 

 small. Oviparous. 



Type Genus. — Strongylus Mueller, 1780 . 



Other Genera. — Triodontophorus Looss, 190 1; CEsofhagostomum 

 Molin, i860. 



