24 ANIMAL COMPETITORS 



It is now understood that the first thing to 

 do when a case of plague is brought to some 

 port in a ship sailing from the Orient is to 

 exterminate the rats of the locality; and the 

 best preventive against this and other afflictions 

 getting a foothold anywhere, is to keep the rats 

 down. The Japanese were quick to take ad- 

 vantage of the new knowledge, and by the fierce 

 crusade they waged against the wharf-rats in 

 their ports prevented a spread of bubonic 

 plague, always threatening them, in the armies 

 they sent into Manchuria. In this way, too, by 

 a vigorous crusade against the animal in Cali- 

 fornia, in which many hundreds of thousands 

 were trapped or poisoned, the plague was re- 

 cently eradicated in San Francisco before it 

 had reached alarming proportions. 



Rats and trichina. But rats disseminate 

 diseases other than bubonic plague. Trich- 

 inosis among swine is probably perpetuated 

 entirely by rats, since trichinae in the hog can 

 result only from its eating the flesh of animals 

 infested with the parasite. The only two an- 

 imals of the farm known to be subject to this 



