318 



THE DOMESTIC SHEEP. 



worm are contained, on the substance of the brain, causes this 

 special result. The sheep turns round and round in small circles, 

 staggers, trembles, stops eating and drinking, is convulsed and 

 finally dies of paralysis or exhaustion. If the head is examined 



there will be found these cysts, 

 drawings of which are taken from 

 Cobbold's Treatise on Internal 

 Parasites. These may contain 

 many of the immature worms, 

 scores or hundreds, attached to 

 the inner surface of the bladder. 

 It is the pressure of these watery 

 bladders, on the substance of the 

 brain, by which the abnormal 

 movements of the sheep are caused. 

 Sheep become infected 

 through the pasture on which 

 they feed, and on which the eggs 

 "of the worm inlay have been 

 dropped by dogs in their dung, or 

 Fig. 4. T Upper Surface of the Brain, f rom water in which the eggs may 

 showing at (a) the Coenui us cere , , . . , . 



bralis cyst. have been washed or deposited in 



any of the many ways possible. 



These egge are taken of course into the sheep's stomach, and 

 there hatching, they make their way by migration into several 

 parts of the body, the eggs doubtless gaining access to the veins 

 are thus distributed, but perish wherever deposited, except in the 

 brain. Once there, the worms begin a migratory expedition in 

 search of a resting place, making galleries through the brain 

 substance, until they grow too large, when they form a large 

 cyst or bladder in which they remain as above mentioned. In. 

 time, the sheep so infested dies, or is slaughtered, when the head, 

 thrown to the dogs, is eaten and these embryos ar swallowed. 

 The history of the worms described in the preceding pages is 

 then repeated, and the segment or eggs of them mature in the in- 

 testines of the dog until they are discharged and are taken once 

 more into the sheep. 



In this larval stage the worm is known as Coenurus cere- 

 bralie. After its first introduction into the brain of its host, it 

 is about as large as a mustard seed, and the disease becomes 

 manifest in five or six weeks after its introduction. It then 

 grows for some months, during which its effects are constantly 

 increasing in virulence until the final symptoms appear and the 

 death of the sheep follows. 



The first symptoms of the disease noticed are dullness, feeble- 

 ness, "heat in the head, redness of the eyes, and hastened circula- 

 tion. The head suffers visibly, being stretched out, turned back, 

 or carried drooping. Then follow spasmodic convulsions or par- 

 alysis. During these manifestations of pain and distress, the 

 sheep makes those typical movements, turning in circles towards 

 the side of the head affected most, or if the parasite is in the cen- 



