Recent Agricultural Publications. 
401 
If several lodge themselves at one time in the brain cavity, the first 
symptoms of gid are usually observed at from the eighth to the 
twentieth day. When the heads of sheep, dead from gid, are de 
voured by dogs, the bladder-worms of the sheep’s brain change to 
the tape-worm, Trenia ccenur^is, inside the dog. 
The symptoms of cephalic gid in the sheep are, at the outset, in- 
difference and weakness, accompanied by an abnormal attitude of 
the head. Sometimes, when there is simultaneous invasion by a 
large number of bladder-worms, the symptoms become exaggerated. 
The head grows hotter, and pressure on it causes pain ; the pulse is 
more frequent, and, acting under irresistible impulse, the animal 
performs automatic movements, forward, to the right or left, in a 
cii'cle, or rotary on one spot, pivoting round a vertical axis passing 
between the collected four limbs. In other cases the animal acts 
as if intoxicated, and often stumbles and falls. At the same time 
the eyes are deviated inwards or outwards, the neck is contorted, 
there is grinding of the teeth, the mouth is foamy, and convulsive 
contractions seize the limbs. This kind of vertigo — the precursor of 
FiG.6. — C(fnurtix after being treille); natural 
kept in alcohol. size. 
gid — is rarely continuous, but most frequently intermittent. At 
the end of four or six months the real symptoms of gid appear. 
The sheep becomes feeble, gradually loses its appetite, and lags 
behind the flock or does not follow at all. When the parasite 
occupies the surface of one of the hemispheres of the brain, the 
animal describes circles which become smaller and smaller, until at 
last, pivoting on itself, and with the straw, hay, or grass twisted 
around its feet in consequence, it falls down. In other instances 
the circles become extended. Some sheep go straight forward, lift- 
ing their feet high, and holding the head low and close to the chest ; 
these are called trotteurs in France, traberen in Germany. 
The malady under discussion must be carefully distinguished 
from false gid, which is produced by the larvse or maggots of the 
two-winged fly, CEstrus ovis (Figs. 7, 8, 9), lodging in the cavities in 
the frontal bone of the sheep’s skull, to which they gain access 
through the nostrils. W'hen affected with this “ grub in the head ” 
the sheep does not move in a circle, whilst there is nearly always 
snorting, accompanied by a discharge from the nose. 
