678 



NEMA THELMINTHES 



It is commonly called the whip-worm, and is cosmopolitan in its 

 distribution. 



Morphology.— The male measures 40 to 45 millimetres in length, 

 and is easily recognized by the spirally coiled posterior end. Its 

 spicule, which lies in a retractile pouch, measures 2*5 millimetres. 

 The female measures 45 to 50 millimetres in length. The ova are 

 oval, brown, thick-shelled, with a pale, clear body at each pole, 

 where the shell is deficient. They measure 50 to 54 by 23 fi. 



Life-History. — When the egg appears in the faeces, it is unseg- 

 mented, and is said to take eighteen months before the embryo is 



250 



1. 



Fig. 308.- — -Development of the Egg of Trichuris trichiura. 

 (After Stiles.) 



fully developed. The egg with the enclosed embryo is then taken 

 in through the mouth in contaminated food or water, there being 

 no intermediate host. The shell is dissolved by the gastric juice, 

 and the embryo reaches maturity in the intestine in about four to 

 five weeks. 



Patliogenicity.— Usually harmless, but may give rise to intestinal 

 disturbance and at times appendicitis. 



Syngamus von Siebold, 1836. 



Strongyles with broad head, mouth with a chitinous capsule. Male with 

 two spicules. Female with two ovaries and a vulva, situate in the anterior 

 part of the body. 



Syngamus kingi Leiper, 19 13. 



King forwarded quite recently a pair of specimens to Leiper purporting to 

 come from a woman living in St. Lucia who suffered from chronic cough, when 

 the worms were expectorated with blood. Leiper thinks that this may be an 

 accidental infection of man with a parasite which is harboured possibly by a 

 carnivore. It differs from S. trachealis, the common nematode of poultry, in 

 the buccal capsules; these in the male and female are on the same level, 

 whereas in 5. trachealis that of the male is more anterior. Mouth capsules 

 terminal . Tail of female bluntly pointed . 



ORDER II. GORDIACEA. 



Nemathelminthes with the intestinal canal always atrophied anteriorly 

 in the adult; head without papillae; two testes, but never spicules in the 

 male ; vulva always united with the posterior portion of the intestine to form 

 a cloaca; rare in man; only accidental parasites. 



These worms are popularly known as horsehairs, and are supposed to 

 cause serious and even fatal disease in man or animals if swallowed. Their 

 pathogenicity has recently been studied by Stiles, who is unable to support 

 the popular belief as to the serious nature of these parasites in man. They 

 are very long, thin worms, like Filaria, which can be found in ditch-water 

 swimming freely or twining round water-plants. 



The body is covered with a well-developed two-layered cuticle. The mouth 

 and the anterior part of the intestine is obliterated. The posterior end of 

 the male is lobed, and without spicules. In the female there are two ovaries 



