i§8 5 .] 
The Parasites of Civilisation. 391 
civilisation,— not exclusively and necessarily to civilisation 
as now existing, but to any and every possible civilisation. 
From this point of view, then, we may divide the organic 
world into several classes. First come those which have 
entered into human civilisation, and assumed a more or 
less important part in it, as domestic animals and cultivated 
plants. As such they minister to our necessities, our con- 
venience, our pleasures, our follies, and our vices. But with 
this important class we have here nothing to do. 
Again, there is a very numerous class of organisms which 
remain outside of human civilisation, and occupy a more or 
less independent position. Such organisms may be hostile 
to us, or neutral, or, even in the result of their life-work, 
friendly. They may be useful or useless from a human 
point of view ; but they have these points in common, that 
they do not lend themselves to domestication or common 
cultivation, but retire from the face of man, and become 
less numerous in proportion as any country is more thickly 
settled and is brought under general cultivation. As 
examples we may mention the wolf, the bear, hyena, wild 
swine, wild ox, hostile to man and long ago extirpated in 
Britain ; the stork, the roller, the golden oriole, harmless or 
even useful, and extirpated also ; the goldfinch, kingfisher, 
“ scarce swallow-tail ” butterfly, and red underwing moth, 
all harmless, but becoming rarer from season to season, and, 
without some capital change in the habits of the public, 
doomed to certain extirpation. 
With those animals and plants which we have named the 
parasites of civilisation — animal and vegetable— the case is 
utterly different. They are all hostile to man, doing him 
great injury either in his person or his possessions. But 
instead of receding from man, or of growing scarcer as he 
becomes more numerous, more powerful, and wealthier, they 
actually “ grow with his growth and strengthen with his 
strength.” This is, in facft, the reason why we term these 
beings “ parasites on human civilisation” rather than simply 
“ parasites on man.” Not a few of them, as we may have 
to emphasize below, are nearly harmless to the wandering 
savage, but formidable to the dweller in cities or in highly 
cultivated plains. 
A peculiarity of these parasites — weeds and vermin — is 
that civilised man, for the most part unwittingly, and we 
may feel sure unintentionally, introduces them into “ new 
countries ” when he goes to settle there, or introduces them 
to his home in the course of trade. In this manner the 
grey or Russian rat has been conveyed round the world. 
