PARASITIC ANIMALS. 



147 



sinuses, of quadrupeds ; certain hydatids are found 

 in the brain, other species in the liver, and, it may 

 be added, in the cellular tissues of 

 the body, in the abdominal cavity, 

 and even in the eyes themselves. 



Let us take, for example, one 

 species of hydatid* which is common 

 in the brains of sheep, and produces 

 the most terrible ravages. How 

 did this parasite become developed 

 there ? And when there, suppos- 

 ing it to produce others of its kind, 

 how are they to get into the brains 

 of other sheep ? The sheep dies, 

 and the hydatid in its brain also 

 perishes ; and as this is invariably 

 the case, one might suppose that 

 with the death of every sheep thus LINGUATULA. 

 afflicted, the race of these hydatids would be extin- 

 guished, but it is not so ; for it is calculated that 

 out of every thousand sheep fifteen will die of this 

 malady the first year of their age, five in the second 

 year, two in the third, and one in the fourth, and 

 so on, generation after generation. It is supposed 

 that " nearly a million of sheep are destroyed every 

 year by this pest of the ovine race " in France only. 



Many have been the theories upon which it has 

 been attempted to explain the origin of these and 

 other entozoa, and to account for their presence in 

 * Csenurus cerebralis. 



