Experiments on the Development of the Liver-fluke. 29 
hatch, and wet enough to let them hatch in water ; and if, 
secondly, there be snails on such damp ground, sheep may get 
the rot there. And ground once infected is not safe again for 
more than one year. 
Fields may be freed from snails and slugs by scattering cab- 
bage-leaves along the sides of the hedges and elsewhere, and 
collecting in the morning the snails which will be found on the 
under side of them. 
Slates, large stones, and boards laid on the ground and slanted 
up so far as to allow the slugs to crawl under them for shelter 
by day, would be similarly useful. 
Pigs will feed on snails and slugs, but ducks, geese, and other 
birds will both collect and consume them. 
Snails and slugs may be prevented from crossing on to a 
pasture by dressing a width of two or three yards round it with 
coal oil or dead oil, a refuse product cheaply procurable from 
gas-works. This could be easily done by dragging a hurdle 
fitted with thorn twigs, or better, with rope swabs or hempen 
tangles, well soaked in coal oil, round the pasture. 
Soot, fine sand, cinders, chaff from barley, tan, or quicklime, 
spread over a belt of ground and kept drv, might prevent snails 
from crossing it into a pasture inside it. These latter recom- 
mendations are specially valuable at the present season, when 
the slugs have scarcely left the protection furnished by hedges 
and broken ground, the specially dangerous character of which 
is indicated by the well-known fact that sheep are peculiarly 
liable to incur the rot by feeding upon roadside strips of 
grass. 
Much has been recommended in the way of dressing the whole 
of a suspected pasture with lime and other chemicals, but what 
will succeed in keeping snails away from it, will probably spoil 
it for sheep, at least for a time. 
(Signed) George Rolleston. 
A. P. Thomas. 
Anatomical Department, University Museum, 
Oxford, June 21, 1880. 
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