POLICE POWER 35 
know beforehand something of his personal rights 
and liabilities. Rats are nuisances because they 
destroy grain and other property worth millions 
of dollars each year in the United States. Scien- 
tific advances have shown that they are active in 
the spread of plague and very likely of other dis- 
eases. They are great travelers. An infected rat 
might easily find his way into a freight car in 
New Orleans, and land in St. Louis or Chicago, 
and there infect other rats, that in turn might in- 
fect human beings. Though there are infected 
rats in New Orleans, it would hardly be suspected 
by the uninitiated that there was danger of con- 
tracting plague in Chicago, and a case might be- 
come well developed before the correct diagnosis 
would be made. So long as it was thought that 
the rat was only a danger to property the state 
officers might very reasonably leave the protec- 
tion of property from this danger to the individual 
owners; but now that the danger to the public 
is known, and it is a danger which lurks unsus- 
pected, the state not only would have a right, but 
it might be considered a duty, to enact laws which 
would restrict the breeding places of those pests, 
and also require the rat-proofing of buildings in 
cities of a given size. 
22. Treatment of Nuisances. A nuisance may 
be prohibited, abated, or regulated. It may be 
prohibited, by a state statute, a city ordinance, or 
by an injunction issued by the court. Violation 
of the prohibition makes the violator subject to 
criminal prosecution. It may be regulated, as by 
ordinances which make the sale of liquor permis- 
sible only within certain hours. More frequently 
