328 Rats and the Balance of Nature. [Sess. 



characterises the race of "Ifus." It matters not what part 

 of the world man may choose for his habitation, it is certain 

 he will be followed by rats. The distance they travel is 

 remarkable ; and, as I lately pointed out in a letter to the 

 ' Scotsman,' they annually made their appearance at Dalna- 

 spidal in Perthshire when the shooting-lodge became tenanted. 

 To those who know this wild mountainous region, and the 

 distance of barren waste-land that intervenes between it and 

 other habitations, it must seem manifest that they are endowed 

 with a marvellous instinct. Eats, as a rule, make their 

 appearance wherever man takes up his abode, and act the 

 part of scavengers by picking up and devouring refuse that 

 finds its way into drains, or is thrown out in the neighbour- 

 hood, and which when in a state of decomposition engenders 

 disease. In this respect rats seem to have been destined to 

 play an important part in the operation of economic laws. 

 Indeed it has been asserted that " the visits of the plague to 

 western Europe and to Britain have ceased froni the very time 

 when rats became plentiful." 



Eats, like all animals that eat flesh, drink a large quantity 

 of water, and sometimes travel a long distance in search of it. 

 It is interesting to see them drinking, — lapping water with 

 their tongues like dogs. Seeing this is their normal habit 

 when on land, it has often struck me as remarkable how they 

 manage to live in the iron holds of ships without water during 

 long voyages. Notwithstanding the filthy character of their 

 suiTOundings, rats are exceptionally clean animals, and are 

 continually licking themselves with their tongues. Strange to 

 say, while almost every bird and beast has a parasite, I never 

 found one of any description on a rat.-*- I find, however, that 

 rats are very subject to tumours of the skin. In a recent 

 experiment I introduced a large rat in a cage trap into the 

 presence of four cats, and he seemed a great deal more 

 interested in licking his feet than in taking the slightest 

 notice of his natural enemies — so much so that the owner of 

 the cats declared he was a tame one. 



While the amount of mischief done to the agriculturist, the 

 game-preserver, and others, by the increase of rats, admits of 



^ I now learn that a parasite is also present on the rat, though sparingly. 

 Jlr Wm. Forgan has found one of these parasites, and has sent me a photo- 

 micrograph of it. 



