Thus we may assume that no animal is free in this respect, and man himself regularly affords hospitality to many of them. We feed some with our blood and our flesh; there are some which lodge on the surface of our skin, others in the interior of our organs; some prefer to establish themselves on children, others on adults. The name alone of some is sufficient to make us shudder, while others live peaceably in some crypt, without our suspecting their presence. Who is there that does not nourish some acari, of the genus _Simonea_, in the membrane of the nose? In fact, man gives a home to some dozens of parasites, and the presence of the most terrible among them constitutes, in certain countries, a condition of health which is envied. The Abyssinians do not consider themselves in good health, 90 except when they nourish one or many tape-worms. Among the animals to which man gives his involuntary 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 intestines, or the blood; nine or ten Nematodes, which inhabit the digestive passages or the flesh. There are also some young Cestodes, named _Cysticerci_, _Echinococci_, _Hydatids_, or _Acephalocysts_, which find in him a _crèche_ 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 inhabitants, 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 intestines 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 passage of the pylorus. Some authors give remarkable instances of the abundance of parasites. Nathusius speaks of a black stork, which lodged twenty-four _Filariæ 91 lobatæ_ in its lungs, sixteen _Syngami tracheales_ in the tracheal artery, besides more than a hundred _Spiropteræ alatæ_ within the membranes of the stomach, several hundreds of the _Holostomum excavatum_ in the smaller intestine, a hundred of the _Distoma ferox_ in the large intestine, twenty-two of the _Distoma hians_ in the oesophagus, and a _Distoma echinatum_ in the small intestine. In spite of this affluence of lodgers the bird did not appear to be in the least inconvenienced.