28 Experiments on the Development oj the Liver-Jluke. 
should be destroyed. A dressing of lime will destroy both the 
eggs of the fluke and the snails or slugs. But upon this point 1 
may refer to a paper which was drawn up by Professor Rolleston 
during last June, and is here appended. 
I hope to have the opportunity of completing my experiments, 
and discovering the cercarian form of Fasciola hepatica, but in 
the mean time it has been considered desirable to publish the 
observations already made. 
In concluding I desire to express my thanks to all those 
gentlemen to whom I have had occasion to apply for assistance. 
I have always found them most courteous and ready in supplying 
all information desired, and in facilitating in every way the 
investigations on their fields. 
A. P. Thomas. 
Jan. 1881. 
Pkevention op Rot. 
There can scarcely be any doubt whatever that for the main- 
tenance of rot in sheep and of a breed of flukes, the presence on 
the same ground of a breed of snails is requisite. It is certain 
that sheep do not get " gid " or " sturdy " if dogs are not used 
for shepherding ; and it is all but, if not quite, as certain that 
sheep will not take the rot if they do not feed on certain pas- 
tures infested with certain snails. Rot and " gid " each depend 
upon a parasite, a different one in each case, but each parasite 
is like the other in requiring, if it is to live its life, to find 
lodgment at two different times of that life in two different 
animals. 
To stop fluke disease, as to stop gid, it is only necessary to 
break one link in the chain of events which make up the history 
of either disease. If we can destroy the snails or slugs, which 
the fluke must inhabit at one time of its life if it is to infest the 
sheep at a later period, we shall stop the rot. 
There are many kinds of snails ; and some on thoroughly dry 
pastures, such as the Downs, have nothing to do with harbouring 
our flukes at any stage of their lives. 
Therefore, if we feed sheep on, or with food from, such pastures 
only, we shall not have rot. 
But in wet seasons almost any pasture may be made 
dangerous by infection. 
And the eggs of flukes may be dropped on to a field not only 
by rotten sheep and oxen, but by hares and rabbits ; and, further, 
we may ourselves carry it there in manure. When once there, 
the eggs may remain as such and do no harm. 
But if, firstly, there is warmth enough to enable them to 
