340 FUNCTIONS AND INSTINCTS. 



they can penetrate through the light clothing 

 worn in that climate, rendering it impossible, 

 at that season, to pass through the woods with- 

 out being covered with blood, Dr. Davy counted 

 fifty on the same person ; no sooner does any 

 individual stop, than, as if they saw or scented 

 him, they crowd towards him from all quarters. 

 From their immense numbers, activity, and 

 thirst of blood, they are the great pest of tra- 

 vellers in the interior. Percival says that the 

 Dutch, in their march into the interior, at dif- 

 ferent times, lost several of their men from their 

 attack. Other animals besides man suffer dread- 

 fully from them, and horses in particular are 

 rendered so restive, when they fasten upon them, 

 as to be quite unmanageable and unsafe to ride. 

 The only way to prevent their attack, is to cover 

 the skin completely. 



The office devolved upon the present tribe, 

 is one which, within certain limits, is beneficial 

 to the animals who are the objects of it though 

 those last mentioned would be inserted in a 

 list of the destroyers of the animal kingdom 

 which contribute to maintain a just balance 

 between the different members of it. The fly 

 that bites the horse prevents it from over- 

 feeding, and so the leeches may be of use to 

 the larger aquatic animals, at the same time 

 that the smaller ones, such as the grubs of 

 insects, must generally perish from the inser- 



