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Let us now say a word about the problem of the rats. The first intimation of rat existence was legendary. Rats from India invaded Europe and around years 1700,, invaded England, Denmark and Norway. It has been conceded that rats have the cause of more untimely deaths among human beings by spreading germs of diseases that are fatal to mankind, than all the wars of the history ( In "Vandals fo the Night".J.L.Nicholas, England, 1948).

Rats and mouses have oestrus each 7 days and pregnancy spend 21 to 28 days. If in the world there were only favorable conditions ( environmental and genetic) how many rats shall exist?

Following Zuschlage ( 1 year) ............................880 individuals

Following Fisher ( in 10 years) ......43.319.698.843.030.344.720 individuals,

or a phantastic number of rats.

The black rat or the ships rats, and the brown rat ( very ferocious) were really a disaster. And we must understand how correct is suppose to be our thesis that the terriers of the type we are studying represented one important soluction to hunt the rats, and they increase significantly the numbers of terriers.

The muskrats ( Ordatra Zibetica) , originally from North America were introduced in England, for commercial reazons, they have a valuable skin. In May, 1932 the Ministry of Agriculture started a program to eliminate them. In 1905, were brought to Bohemia (Austria) 2 males and 5 females muskrats. In 1927, half of Austria and the cities of Vienna and Munich were invaded. It was bellivable that they produced one hundred million of voracius creatures ( In "Combate aos Ratos" Eurico Santos. Ministério da Agricultura, Brazil, Rio, 1948).

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