144 BACTERIOLOGY FOB NURSES 



These experiments suggest practical measures for 

 the control of plague. Rats, fleas, and filth being 

 closely connected, it remains for those concerned 

 to remove these causes. Such measures may be 

 easily employed in Europe and America, but in China 

 and India, whose inhabitants Uve in unspeakable 

 filth, it will require generations of education to re- 

 move the conditions which so strongly favor the 

 development and spread of the disease. 



Plague in Animals. — Rats, mice, guinea pigs, 

 and ground squirrels are very susceptible to plague, 

 and monkeys are particularly sensitive to artificial 

 inoculation. Rats and guinea pigs may be infected 

 by feeding. Dogs, swine, cattle, and horses may be 

 inoculated artificially, but do not contract the disease 

 under natural conditions. 



As before stated, the plague of rats has been the 

 subject of widespread investigations, which have 

 led some observers to declare that plague is primarily 

 a disease of rats, not man. 



Protective and Curative Sera. — "Haffkine's 

 prophylactic" serum has been used as a preventive 

 of plague in India to a considerable extent and 

 degree of success. 



The statistics of Punjab in 1902 report that among 

 the inoculated 1.8 per cent became infected, while 



