472 THE DISEASES AND DISORDERS OF THE OX. 



districts there may be an annual loss due to this cause of about 

 7| per cent, among yearling sheep. In fact, the malady is rarely 

 met "with in sheep above two years old, and it usually affects 

 lambs which are under one year of age, and only rarely occurs 

 in sheep over eighteen months old. It is said to be more fre- 

 quently met with in the case of some breeds, such as the Cheviots, 

 than in that of others, and particularly in the autumn and winter 

 it afflicts animals which are already enfeebled. In some districts, 

 however, it apparently breaks out most especially in the summer 

 time, provided that the sheep are kept upon unenclosed pastures, 

 where the flocks are constantly under the guardianship of shep- 

 herds aided by dogs, or on farms where sheep are fed to a great 

 extent on turnips, being confined within short limits, and having 

 one or more dogs among them. 



The Ccenurus cerebraliSy the larval form of the Tcenia 

 ccenurus of the dog, is the hydatid which gives rise to the 

 disorder known as gid in the sheep. It has also been found in 

 the goat and in the ox. Only one instance of it being found in 

 the horse has been recorded. This hydatid varies in size from tliat 

 of a pea to much larger than a pigeon's egg, and it is like a bladder 

 provided with spots, which in reality are retractile heads, each 

 of which is furnished with hooks and suckers. A single bladder 

 may have from three to five hundred heads. The vesicle is full 

 of a pale fluid, and its walls consists of three layers. As it 

 increases in size, it presses more and more on the walls of the 

 skull, and in consequence of this the cranial bones become so 

 thin and soft that they can easily be found and pierced, especially 

 as they may probably yield in some degree to the force exerted 

 from within by the gradually enlarging cyst. 



Formerly, sturdy was thought to be due to a fly perforating 

 the skulls of sheep and laying its egg or eggs in the brain. It 

 is now, however, well known that this disease is occasioned by 

 the eggs of the tapeworm infesting a dog being taken up by the 

 sheep from the ground, and by their getting into the blood and 

 finding a favourable place of development in the brain of a lamb 

 or sheep. The eggs are distributed on the ground by dogs 

 afflicted with the tapeworm called the TcBnia ccenurus. Dogs 

 which have eaten the hydatids taken from the brains of sheep 

 afflicted with sturdy soon develop large numbers of taenise, and 

 on giving the joints which were deposited by dogs thus treated 



