Experiments on the Development of the Liver-fiulic . 23 
Oxford, the rot has followed the geological character of the 
ground very closely. All fields upon the Oxford Clay have 
been dangerous, whether exposed to floods or not. On the 
other hand, floods on low porous ground or on gravel appear to 
do no harm, unless the water stands for a long time. AH this 
is easily intelligible when we remember the necessity of moisture 
for the hatching of the embryo. Winter floods are not neces- 
sarily dangerous, because warmth is required as well as wet. 
Surprise is sometimes expressed at the way in which the rot 
breaks out in a wet season suddenly in isolated flocks. The 
eggs of the fluke must be present on the ground, or rot cannot 
occur, but the distribution may take place in many ways, as by 
floods or running water, or in manure. Rabbits also have much 
to answer for in distributing the parasite. Everywhere about 
Oxford the same account is given of the way in which these 
animals have suffered from the rot, and in some neighourhoods 
they have almost been exterminated. I have received livers of 
fluked rabbits and have found them to contain as many as forty 
or fifty flukes. Wherever they go, and they often wander far 
from home, the eggs of the fluke are distributed in their 
droppings, aud the first condition for the existence of rot is 
satisfied. 
Practical men seem to have come to the conclusion that the 
rot is particularly due to close grazing, and that those animals 
suffer most which can bite the nearest to the ground. A sheep 
can graze where cattle or horses can get nothing (indeed, it can 
graze closer than any other animal except a kangaroo), and 
some farmers ascribe to this cause the special liability of sheep 
to fluke-disease. " Hog-jawed " sheep are known to escape the 
rot when all the rest of a flock take the infection. Lambs suffer 
more than older sheep, and this may be due to lesser digestive 
power, which does not enable them to digest the germs of the 
fluke ; but one good observer has told me that at Michaelmas of 
the year in which a lamb is born, it can graze closer than an 
older sheep, quite down into the roots of the grass, and would 
do fairly well where an old ewe would starve. Hence he 
attributes the liability of lambs to rot partly to their grazing so 
closely. This generalisation, if true, indicates that the germ of 
the fluke is picked up close to the damp roots of the grass. 
But whilst the general conclusions to be drawn from the 
accounts of untrained observers are often valuable, and afford 
suggestions for accurate research, there is much danger in 
accepting them too quickly. Extreme difficulty is often met 
with in eliciting the truth in matters of fact, and the following 
instructive instance shows the necessity for the utmost caution 
in making enquiries. A remarkable case of sheep-rot was heard 
