solutions are destructive
not only to fluke embryos but to snails. This application is to be made
during the summer months at the rate of about 500 to 1,000 pounds of lime
per acre. The same authors also recommend extract of male fern for the
treatment of fluke disease. Moussu states that the average dose for cattle
is 1 gram of the extract for each 10 kilograms of live weight; that is, 10
grams for a young animal weighing 100 kilograms (about 220 pounds) up to
50 grams as a maximum for large animals weighing 500 kilograms (about
1,100 pounds) or more. The extract is mixed with about 5 times as much
non-purgative oil and the dose is administered each morning for five
consecutive days two hours before the animal is allowed to feed after
having been fasted over night. The extract of male fern used should have a
guaranteed strength of 22 to 25 per cent of filicine and 3.5 per cent of
filicic acid.

[Illustration: FIG. 19.--The common liver fluke (_Fasciola hepatica_).]

[Illustration: FIG. 20.--The large American fluke (_Fasciola magna_).]

[Illustration: FIG. 21.--Portion of grass stalk bearing three encysted
cercariae of the common liver fluke (_Fasciola hepatica_). Enlarged.]

TAPEWORM CYSTS OF LIVER AND OTHER VISCERA.

Three kinds of tapeworm cysts are found in the viscera of cattle. One of
these (_Multiceps multiceps_, or _C[oe]nurus cerebralis_) will be further
referred to in the discussion of gid (p. 528). All these are the
intermediate stages of tapeworms, which live when mature in the intestines
of dogs, wolves, and other canines. The eggs of the tapeworms are scattered
over the fields in the droppings of infested dogs or wolves, and when
swallowed in food or water by cattle hatch out and the embryos migrate to
the liver, mesentery, lungs, brain, or other organs, where they develop
into cysts, variously known as hydatids, bladder worms, water balls, etc.
When organs of cattle thus infested are eaten by dogs or wolves the cystic
worms are also liable to be swallowed and then develop into mature
tapeworms. To prevent cattle from infection with these parasites stray
dogs, wolves, and coyotes should be killed wherever found, and dogs too
valuable to kill should be kept free from tapeworms. As a precaution
against infection with tapeworms, the viscera of cattle, sheep, or hogs
should not be fed to dogs unless cooked.

HYDATIDS (_Echinococcus granulosus_) form tumors (fig. 22) of varying size
(sometimes