Photograph from U. S. Public Health Service 



WRECKING A BUILDING IN THE CENTER OP THE NEW ORLEANS PLAGUE DISTRICT 



When New Orleans was threatened with bubonic plague buildings were razed to the 

 ground in the effort to- exterminate the rodents which carried the germs of the dread dis- 

 ease. The structure shown above was a combined stable and junk warehouse, which, with 

 several other buildings, was surrounded by a two-story brick wall. In the inclosure there 

 was a small house for the stableman, the ground floor of which was only six inches above 

 the level of the court. When this floor was removed 54 of the total of 86 rats captured 

 during the wrecking of all the buildings were killed, and of these 20 were found to be 

 plague infected. 



where they find the harvested crops 

 ready for their consumption. 



When the food supply suddenly de- 

 creases, following a period of plenty dur- 

 ing which the rats have greatly increased 

 in numbers, a migratory impulse appears 

 to affect the entire rat population over 

 large areas and a general migration takes 

 place. At such times the rats are extra- 

 ordinarily bold, swimming rivers without 

 hesitation and surmounting all other nat- 

 ural obstacles. The first invasion of Eu- 

 rope, when rats swam the Volga, was an 

 instance of this kind. Experiments by 

 the U. S. Public Health Service have 

 shown that when released in the water of 

 a harbor rats may swim ashore for a dis- 

 tance of 1,500 yards. 



An observer in Illinois, who saw a 



more local migration, states that he was 

 passing down a road in the moonlight 

 one night in the spring when he heard 

 a rustling in a field near by. Soon a 

 great army of rats swarmed across the 

 road before him, extending as far as he 

 could see. This district afterward suf- 

 fered severely from the presence of these 

 pests. 



The extent to which rats wander from 

 centers of abundance was well illustrated 

 in New Orleans by experiments of our 

 Public Health Service. One hundred 

 and seventy-nine marked rats were re- 

 leased at a point in the residential part 

 of the city. In less than 60 hours one of 

 the marked rats was captured in a trap 

 about a mile from the point where it was 

 liberated, and within two weeks others 



