90 ANIMAL PARASITES AND MESSMATES. 



consider themselves in good health, except when they 

 nourish one or many tape-worms. 



Among the animals to which man gives his involun- 

 tary assistance, we may mention first, four different 

 Cestoidea, or tape-worms, which live in the intestines ; 

 three or four Distoma, which lodge in the liver, the intes- 

 tines, or "the blood; nine or ten Nematodes, which inhabit 

 the digestive passages or the flesh. There are also some 

 young Cestodes, named Cysticerci, Echinococci, Hy- 

 datids, or Acephalocysts, which find in him a creche to 

 shelter them during their life. These always choose 

 enclosed organs, like the eye-ball, the lobes of the brain, 

 the heart, or the connective tissue. We also provide a 

 living for three or four kinds of lice, for a bug, for a 

 flea, and two ascarides, without mentioning ' certain 

 inferior organisms which lurk in the tartar of the teeth, 

 or in the secretions of the mucous membrane. 



There are some animals which harbour few inhabi- 

 tants, while there are others that keep up a great retinue ; 

 and it is not always, as we have already said, that those 

 who give lodging to but few enjoy the most excellent 

 health. We might give as an instance of this, a fish 

 which is known to all, the turbot, which as well as the 

 woodcock is highly prized, though both have their in- 

 testines literally obstructed by tape-worms and their 

 eggs. We have never opened one, large or small, lean 

 or fat, which had not its intestines filled with cestode 

 worms. They are so numerous as to form a kind of 

 cork, which one might think intended to close the pas- 

 sage of the pylorus. 



Some authors give remarkable instances of the abun- 

 dance of parasites. Nathusius speaks of a black stork» 



