THE LIVER-FLUKE. 37 



small prickles, directed backwards, which one can easily feel on 



pulling the worm through the fingers from tail to head. The 



oral sucker is terminal, small, and round ; 



' ' ' o — - 



the ventral sucker is towards the anterior 



end, large and round, with a triangular 



opening. The intestine can be seen 



through the integument as two dark fi--y5V H^li 



forked branches. The ova, which may '*""''' v 



often be seen in the uterus, are ovoid 



bodies of a dark-brown colour. 



Lambs are especially affected. The 



Fig. 7. — Liver-fluke 



same species is found in goats, cattle, (Distoimmhepatuam). 

 camels, the horse, pig, rabbit, and man. ., ". Oral sucker ; gp, gen- 



' 7 1 oj ' italpore; c, ventralsucker : 



They live chiefly in the biliary ducts of p''. I'liarynx ; a, alimentary 

 the liver. Damp wet seasons and damp 

 ground favour the spread of distomatosis. Fields liable to be 

 flooded along the course of rivers are often certain to cause sheep 

 to be infested with Fluke, the cysts being spread over the grass 

 when the floods are out, and afterwards taken in by the lambs. 



Life-Msiory. — The life-history of this species has been deter- 

 mined by Leuckart and Thomas. The ova pass out from the 

 bile-ducts through the intestine to the ground in the excreta. 

 Each ovum is provided with a lid, which breaks off, and the em- 

 bryo is released. Incubation takes place in the summer, and 

 occupies from three to six weeks. The embryo is covered with 

 fine hairs — cilia — and is known as the ciliated emh-yo (fig. 8, a). 

 It is lanceolate in form, broadened in front, and provided with 

 a curious boring apparatus at the anterior end. It is necessary 

 that this embryo should meet with its first host within twenty- 

 four to thirty hours after it has hatched. Should it not do so it 

 dies. Its first host is one of the water-snails {Limnuius) that we 

 see in such abundance along the sides of streams, runnels, and 

 dykes. If the embryo comes in contact with one of the Limnffii, 

 it bores its way into its body by means of the anterior process, 

 and then enters the respiratory cavity. The commonest host in 



