as large as 6 inches in diameter) in the liver, lungs, and other
organs. Their contents are liquid, resembling water. The presence of these
parasites can not be detected in the living animal and there is no
medicinal treatment for them. Organs containing hydatids should be
destroyed by burning in order to prevent their being eaten by dogs. This is
especially important, as dogs infested with the tapeworm stage of this
parasite are a menace to human beings on account of the danger of infecting
them with hydatids, which develop in man if the eggs of the hydatid
tapeworm are swallowed.

THIN-NECKED BLADDER WORMS (_Taenia hydatigena_, fig. 23) are most commonly
found attached to the mesentery and omentum. There is no medicinal
treatment.

GID.--Bladder worms (_Multiceps multiceps_, or _C[oe]nurus cerebralis_),
which are occasionally found in the brain of cattle and cause gid,
"turnsick," or "staggers," deserve mention, as they are rather common among
sheep in the Northwest. As already alluded to, these worms are the
intermediate stage of a tapeworm found in dogs, and their life history and
the means of preventing infection have been briefly discussed above (see p.
527).

Cattle harboring this parasite show symptoms indicating an affection of the
brain, walking or turning in circles, dizziness, uneven gait, impaired
vision, etc.

Treatment consists in trephining the skull and removing the parasite, an
operation which requires a skillful operator and is frequently
unsuccessful. Unless the parasite is removed affected cattle almost
invariably die.

[Illustration: FIG. 22.--Hydatids (_Echinococcus granulosus_) in portion
of hog's liver.]

[Illustration: FIG. 23.--Thin-necked bladder worm (Taenia hydatigena)
from abdominal cavity of a steer.]

TAPEWORM CYSTS IN THE MUSCLES, BEEF MEASLES.[19]

Small tapeworm cysts (_Taenia saginatae_), about the size of a pea, found in
the muscles of cattle are the larvae of the common tapeworm of man. Cattle
become infected from feed or water which has been contaminated by the feces
of persons harboring the adult tapeworms, and human beings in turn become
infected by eating raw or rare beef infested with the larval stage (measly
beef).

To prevent cattle from becoming infested with this parasite care should be
taken that human feces are not placed where they will contaminate the feed
or drinking water.

This parasite i