TREMATODA 



559 



The Distome cercarice may be identified as follows : — 



A. Tails shsQnt— Cercarice. 



B. Tails present : — 



1. Tails stumpy — Monocercous. 

 II. Tails well developed: — ■ 



(a) Tails joined, forming colony — Rattenkonig cercaricB. 

 ih) Tails not so joined : — 



1. Tails set with spines — Trichocercous. 



2 . Tails not set with spines : — 



(a) Tails forked at end — Furcocercous. 



(b) Tails not so forked: — 



(c) Base of tail forms spaceTnto which body 



can be drsiwn—Cystocercous. 



(d) Base of tail forms no such space: — 



(e) Tail as wide or wider than body — • 



Rhopalocercous. 



(f) Tail narrower than body — Lepto- 



cercous. 



The Leptocercous cercarice may be further differentiated as 

 follows : — 



A. Body armed anteriorly :— 



1. With collar and crown of thorns— Echinostomes. 

 11. With a stylet — -Xiphidiocercarice. 



B. Body unarmed anteriorly — Gyntnocephalous cercarice. 



Habitat— These parasites are found in all classes of the verte- 

 brates, and may occur in any of the organs, but the most common 

 in man are those of the liver, the intestinal tract, the lungs, and the 

 urinary bladder. It is important to remember that the adult 

 parasites may live in domestic animals, especially in cats, that 

 they may affect pigs and cattle, that development takes place in 

 snails, and that the cercaria are free-swimming, but encystment on 

 grass, water- weeds, etc., must be borne in mind. 



Pathogenicity. — -Apparently the smaller forms can live in human 

 beings without being suspected, but irritation of the bladder, liver, 

 intestine, and lungs may result either as the effect of the eggs or of 

 the parasite. 



Diagnosis. — The systematic examination hy the microscope of 

 the faeces after centrifuging, especially in cases of diarrhoea, and of 

 the urine and sputum, is the only certain method of diagnosis. 



Treatment. — ^The treatment of infections by these animals is 

 little studied, but Christopherson has lately recommended Tariar 

 Emetic [vide Chapter LXXIX., and more especially Chapter 

 LXXXII.). One may try to kill or expel the intestinal forms by 

 chloroform mixed with eucalyptol or Chenopodium followed by 

 purgation, as described in Chapter "LXXV. (Ankylostomiasis), or by 

 extract of male fern all in the same chapter (Tseniasis). 



Prophylaxis. — We do not know enough about the life-cycles to 

 lay down general rules about prophylaxis, but it will be obvious 



