400 Recent Agricultural Fuhlications. 
Gid in Sheep. — Hydatido-cephalus, or “ gid,” is exclusively due 
to the presence in the nerve centres, and particularly in the brain, 
of Coenurus cerebralis, which is the bladder-worm stage of the tape- 
worm, Tcenia coinurus, of the dog. It is common in the sheep, 
less frequent in the ox and goat, and quite exceptional in the horse. 
The malady appears to be not so prevalent in England as formerly, 
though in certain seasons it may cause considerable damage, some- 
times as many as 35 per cent, of the flock being lost. In addition 
to gid, the disorder has 
received such names as 
turnsick, turnside, sturdy, 
goggles, turn, blob-whiil, 
giddiness, punt, hydatid 
on the brain. 
Gid has its origin in 
the Tamia ccenurus (Fig. 5) 
of the dog. The mature 
segments of this tapeworm, 
gorged with ova, are ex- 
pelled with the excre- 
ments, and fall upon the 
herbage of the pastures 
where the dog wandei’s 
beside the ruminants which 
he guards. The segments, 
decomposing on the ground, 
allow the contained ova or 
eggs to escape, and the 
rains disseminate these 
over the grass, or wash 
them into ditches or ponds 
from which animals drink. 
As humidity favours the 
ova, gid is more common 
in flocks that frequent 
damp pastures, and also 
when the spring and 
summer have been rainy. 
Lambs and hoggets are 
chiefly aflected, the disease being of exceptional occurrence in 
sheep of more than two years old. When a lamb swallows the 
ova of Twnia cmnur^is, the shells of the minute eggs soon 
dissolve in the gastric juice, and the embryos are set free. Aided 
by their six hooks, the latter pass through the walls of the 
stomach or intestine, wander among the tissues, very probably 
penetrate some vessel, and are carried in the current of the blood to 
various parts of the body. Those which arrive at the nerve centres 
are almost the only ones to pursue their development. They then 
lose their hooks, and are transformed into vesicles that gradually 
acquire the character of the bladder- worm, Gosnums cerebralis (Fig. 6). 
