204 



DISEASES OF SHEEP. 



ing the truly important points in the disease. For 

 this reason, I hold them worthy of particular descrip- 

 tion ; as it is only by becoming acquainted with their 

 history and habits that we can form correct ideas either 

 of their mode of origin or of their supposed ability to 

 cause rot. 



(162.) The Liver Fluke ffasciola hepatica or dis- 

 toma hepaticum. Fig. 6. Plate I.) derives its name 

 from the resemblance it bears to the plaice or flounder, 

 though its shape has been more aptly compared to that 

 of a melon seed. It is flat and oval, of a brownish- 

 yellow colour, and varies in size from that of a pin-head 

 to one inch in length, and half an inch in breadth. 

 Each worm is bisexual or hermaphrodite, on which 

 account they multiply with great rapidity. The generic 

 name — distoma — signifies having two pores, a. h» 

 Fig. 6, Plate I., and is for this reason applied to it. 

 The nipple-like body at the extremity a. contains the 

 orifice of the pore or opening leading to the female 

 division of the generative apparatus, situated between 

 a. and b. In this cavity are formed the eggs, which 

 are at intervals protruded, to be hatched when floating 

 in the sheep's bile. The male organ is situated in 

 front of the ventral pore. The anterior opening b. is 

 equivalent to a mouth, and leads inwards and back- 

 wards, communicating with the intestinal canals c, 

 which are easily made out in the recent animal, from 

 their containing dark bile, and which, as in other crea- 

 tures low in the scale of being, serve the double pur- 

 pose of a digestive and circulatory apparatus ; that is 

 to say, the stomach first prepares a fluid which is equi- 



