as Enemies of Mankind. 



13 



and twenty-three have been recorded ; and Lantz thought it safe 

 to conclude that the average is not less than ten per litter. Newton 

 Miller's experiments gave an average of between ten and eleven, 

 the number per litter ranging between six and nineteen ; his 

 evidence also showed that the females produce five or six litters 

 annually. 



The young are born in a helpless condition, being blind, naked 

 and pink, with their external ears sealed down. Their eyes open 

 at about the fourteenth day, and they are weaned in the course of 

 their fourth week. 



THE ECONOMIC IMPOETANCE OF EATS. 



We have now to consider rats from an economic standpoint. 

 In such discussions we usually find two sides to the account — 

 credit and debit. Unfortunately there is practically nothing that 

 can be placed to the credit of either i?. rattus or B. norvegicus. 

 Their activities as scavengers are no longer of the slightest benefit 

 to humanity ; the most that can be said for either perhaps is that 

 they may keep the numbers of House Mice to some extent in check. 

 On the other hand, the debit account is long and deplorable. 



Damage occasioned by rats. — That rats do great damage 

 to property and materials of all kinds is a fact only too well 

 known to the public. Therefore, there is no need to review in 

 detail all the misdeeds of these animals ; we may be content with 

 mentioning some of the chief heads of damage. 



Property. — By burrowing under foundations, through walls 

 and embankments, and by gnawing their way through partitions, 

 doors, and joists rats cause great damage to property. Such 

 operations have sometimes led to serious structural collapses and 

 considerable monetary loss. By gnawing through gas and water 

 pipes they occasion great inconvenience and sometimes serious 

 danger ; by carrying matches into their combustible nests and 

 igniting them, and by gnawdng away the insulation from electric 

 lighting wires, they have caused destructive outbreaks of fire and 

 sometimes the death of the human residents. 



Materials and Food. — In docks, warehouses and shops, and 

 while in transit by rail or sea, large quantities of merchandise, of 

 the most varied description, are annually destroyed or more or' 

 less seriously damaged by rats. In houses, hospitals, and other 

 institutions they display a most catholic taste — food, furniture, 



