828 PARASITIC DISEASES. 



one year old, sheep above two years old being rarely affected. 

 It prevails to a great extent on unenclosed lands, and for the 

 reason that shepherds have to be assisted by dogs, whilst on 

 enclosed pastures, and where sheep are unattended by dogs, the 

 disease is scarcely known. 



Sym.ptoms. — The usual form of sturdy is that due to the location 

 of a hydatid in one of the cerebral hemispheres. The sheep so 

 affected, when caused to move, turns from right to left, or left to 

 right, as the case may be ; but when the parasite is lodged be- 

 tween the hemispheres, the animal steps high, and goes forward 

 in a straight line ; the head is then carried upwards, and there 

 may be a varying degree of amaurosis in one or both eyes. 

 Sometimes the animal becomes both blind and deaf, and is un- 

 able to follow its companions. When the hydatid is lodged in 

 the cerebellum, the animal's movements are performed without 

 control. The head is elevated ; the limbs are moved with diffi- 

 culty and automatically ; one or two stej)s are taken forward, 

 when the animal starts with a bound, but immediately falls, and 

 is unable to rise for a time. 



Wlien the animal is first affected the symptoms are generally 

 severe, from the congestion and irritation ; as the contents of the 

 skull adapt themselves to the hydatid, the brain symptoms sub- 

 side more or less ; but as the parasite grows, the symptoms 

 become more severe, until paralysis is induced, and the animal 

 can no longer stand. 



As many tumours and hydatids of different species are found 

 in the brain which do not induce symptoms of sturdy, Davaine 

 believes that the nervous substance is irritated by the heads of 

 the parasite, which protrude from the bladder, and by means 

 of their hooks and sucking discs penetrate the brain substance 

 nearly two lines in depth. As the ccenurus grows, the animal 

 becomes more and more emaciated, and death occurs, unless the 

 sheep be relieved naturally or artificially. The natural method 

 is by the bones of the skull becoming absorbed, the skin acci- 

 dentally broken, and evacuation of the hydatid. This is, however, 

 very rare. 



The bones of the skull, however, are generally softened, and 

 if in about three weeks after the first manifestation of the 

 symptoms the head be pressed with the thumb, a remarkable 

 degree of softening will be found at one part of it, as if the skull 



