GID STURDY TURNSICK. 215 



spot and refuse to move on ; hence have arisen the terms by 

 which the malady is commonly known. Gid is essentially 

 a form of animal parasitism, and owes its origin to the 

 presence of one or more cystic or bladder-like parasites in 

 the substance of the brain, and to this fact the giddiness and 

 disordered movements of the infected lambs are due. 



How these cestoid worms, as they are termed, obtain an 

 entrance to the body can only be shown by relating a short 

 biological story. The gid parasite consists of an hydatid, 

 or sack, filled with a watery fluid, and is sometimes spoken 

 of as a bladder-worm. It varies in size from a hempseed 

 when young to that of a cricket ball when matured. These 

 bladder-worms are derived from a tapeworm (tania ccenurus) 

 which infests the dog, and are in reality the young or larvae 

 of that creature. Just as the maggots which we find in 

 flesh represent the young of the blow-fly, so do these hydatids 

 in the brains of lambs represent the infant stage in the 

 development of the tapeworm. Each hydatid, however, 

 represents not one but a brood of many larval tapeworms. 

 How many may be known by counting the little white spots 

 which are seen scattered over the wall of the bladder, and 

 which are in fact the heads from which future tapeworms 

 are to spring should they find their way into the bowels of 

 the dog. Without the dog and other members of the species 

 to which he belongs there could be no gid parasites, and 

 consequently no giddy sheep. The lamb acts towards the 

 bladder-worm as a host, i.e. t it affords it shelter and nourish- 

 ment in its youth until fitted for its new habitation in the dog, 

 where it proceeds to throw out segments and complete its 

 development into tapeworms. Without sheep and others of 

 the species to nurse the bladder-worm, there could be no 

 tapeworm. Neither the hydatid nor the tapeworm can be 

 regarded as welcome guests. The former by its growth and 

 expansion breaks down the brain and paralyses its host, 

 while the latter reduces the dog it infests to starvation by 

 disordering the digestive canal, and not unfrequently proves 

 suddenly fatal by exciting fits of epilepsy. 



