Experiments on the Development of the Liver-fluke. 27 
could only have been got rid of, there was nothing to preclude 
the possibility of the liver being again serviceable. But on the 
other hand, there w<as nothing in the appearance of the flukes to 
suggest that they were drawing near the natural limit of their 
lives. Both digestive and generative organs were in full func- 
tional vigour, the oviduct was filled with eggs, and there was no 
indication of any exhaustion of the supply. The ewe had been 
kept under conditions which render re-infection highly im- 
probable, and it follows, therefore, that tlie life of the liver-fluke 
may extend beyond one year. 
Conclusion. — The necessary conditions for the existence of rot 
in any given locality where sheep are kept are (1) the presence of 
the eggs of the fluke, (2 )water or wet ground during the warmer 
months to enable the embryo to hatch out of the egg, (3) the 
presence, it is believed, of slugs or snails upon the ground to 
secure the further development of the embryo and the production 
of the cercarian form which eventually enters the sheep. 
If any one of these conditions be not satisfied, there can be no 
rot. Very little attention is paid to the eggs of the fluke, but 
these, like the eggs of all entozoa, should as far as possible be 
rigorously destroyed ; if we can effect this we shall prevent the 
rot. The eggs are present in immense numbers in the droppings 
of infected animals, and hence are distributed wherever such 
animals are kept. Unless sheep are very valuable it may be 
better to kill them instantly they are known to be infected ; for 
we shall thus prevent the production of more eggs and the 
propagation of the fluke. The cure of the sheep, if cure be 
possible, will probably cost more than it is worth. If rotted 
sheep are kept in a yard, the manure should be collected, and 
never spread upon damp ground. The eggs may be hindered 
from developing by adding a little coal-tar oil to the manure, and 
keeping it for some time before it is spread on the fields. Or, the 
manure may be spread on dry, well-drained ground. Above 
all, livers of fluked sheep should be destroyed, for if every egg 
succeeded in producing one fluke, a single liver might contain 
sufficient eggs to destroy a flock of 50,000 sheep. Fortunately 
the chances are immensely against any egg giving rise to an 
adult fluke, but we should do all we can to increase these adverse 
chances. 
With regard to the second condition for the existence of rot, 
the obvious remedy is that the land should be thoroughly drained. 
The third condition is the presence of slugs or snails. It has 
not been possible as yet to prove the presence of the cercaria 
of the liver-fluke in one or more particular slugs or snails, but 
for reasons already given, there is no ground for doubting its 
existence. Hence all slugs or snails on sheep-rotting fields 
