LIVER FLUKE. 313 



in pastures that are low and swampy, or which are 

 subject to inundation. They say that it is chiefly 

 after a wet summer or autumn that the disease 

 shews itself; that on such occasions, particularly 

 in marshy districts, it generally prevails to a greater 

 or less extent ; but some think that if the rains do 

 not abound until the winter's frost is over, the sheep 

 are not so liable to it. Feeding sheep for a very 

 short time in wet pastures is sufficient to bring 

 on the disease : a relation tells me, that, some 

 years back, his flock contracted the disease by only 

 one day's feeding upon a wet moor. This account, 

 on the whole, seems to favour the opinion that 

 these worms are bred in the water, and adhering 

 to aquatic grasses, either in the egg, or, as it may 

 be termed, the larva state, (in which last state they 

 may possibly differ greatly from the adult fluke,) 

 are swallowed by the sheep.* The greater part 

 of these worms may perhaps be destroyed by the 

 frost of winter, which would serve as a reason 

 why there are less apprehensions of this disease 



* The following case, recorded by Dr. Watson, seems to con- 

 firm the idea of these worms being swallowed by the sheep in the 

 first instance, in some state or another : "A healthy flock of sheep 

 were driven through a considerable tract of country, and one of 

 them on the way broke its leg, and had to be carried on horse- 

 back. For one night the flock, with the exception of the maimed 

 one, rested in a marshy meadow, and every individual was seized 

 with the rot but itself; it escaped the disease, and had no liver 

 fluke. May it not be assumed, that the flock swallowed the eggs 

 of the fluke with the fodder they cropt from the moist meadow?" 

 I have copied this from the volume of Reports on the progress of 

 Zoology and Botany, recently printed by the Ray Society, p. 291. 



