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CHAPTER XII. 

 TRICHOTRACHELID^E. 



THE family Trichotrachelidce are distinguished by the 

 anterior part of the body being long and thin, whilst the 

 posterior is broader and rounded posteriorly. The anus 

 is terminal. The oesophagus is long and straight without 

 any expansions. 



The females have only one ovary and the genital pore 

 or opening of the ovarian tube is situated at the junction 

 of the thick posterior part with the thin anterior. In the 

 males there is only one spicule and the vas deferens 

 opens into the cloaca. 



There are two genera, represented by one of each 

 species, in man Trichocephalus and Trichinella. In 

 Trichocephalus the anterior part is very thin and thread- 

 like, and the junction with the thicker posterior part is 

 abrupt. They are vulgarly known as whipworms. The 

 eggs are oval and have a thick outer capsule, brown in 

 colour, with an opening at each end. Development is 

 direct, the embryo is slowly developed in the shell and 

 when the eggs containing these larvae are swallowed by 

 man the shell is dissolved off and the larvae are set free 

 and attach themselves to the intestinal wall and become 

 sexually mature. No alternative host is required. Various 

 species of Trichocephalus inhabit the intestines, either 

 the large or small intestine, of mammalia. That in dogs 

 is known as Trichocephalus depressiusculus. 



Trichocephali also occur in several species of monkeys, 

 in cats, &c. 



In man one species is known, the Trichocephalus 

 trichiurm or T. dispar. 



