29 



of the muscles. The attack lasted a few days or a week, and 

 was followed by similar attacks at intervals of from three to 

 ten days. These intermittent symptoms in some cases extended 

 through several months.^ 



The most serious indictment against the rat is the destruction 

 of human lives caused by it as a carrier of diseases fatal to 

 mankind. The deadly bubonic plague is com- 

 municated to man mainly by the rat flea. The 

 infection is conveyed from rat to rat, and from 

 rat to man solely by the rat flea. The conclu- Germs, 

 sions of the India Plague Commission have proved this. There 

 is some reason to believe that certain Asiatic marmots carry 

 the bacillus and some Asiatic and American squirrels have been 

 infected, but the chief distributing agent is the rat. Professor 

 Lantz states that within a dozen years there were 5,000,000 

 deaths from the plague in India, and in 1897 the plague de- 

 stroyed 1,200,000 natives of that country. By the year 1908, 

 the present pandemic of the disease, which started in China in 

 1894, had invaded every continent and secured a foothold in 

 51 countries. Already (1914) it has reached the United States in 

 Hawaii, San Francisco, Seattle, Porto Rico and New Orleans. 

 With the increase in traffic at the port of Boston, there is con- 

 stant danger that it may be brought here by ship-borne rats. 

 Probably no seaport is now safe from this pestilence, and the 

 only known method of combating it is to isolate all patients 

 and to extirpate rats. In the campaigns against the rat, build- 

 ings have been razed and burned, and all ships in infected ports 

 ^s^^^ have been fumigated to destroy rats, 



and many people have been engaged in 

 hunting, trapping and poisoning them. 



This infection does not persist in the 

 soil and a case of bubonic plague in 

 man is not in itself infectious. The nonepidemic season is 

 bridged over mainly by acute plague in the rat. Where there 

 are no rats there are no rat fleas, and, therefore, there is no 

 plague.^ 



Trichinosis among swine, a dreaded disease fatal to human 

 life, is disseminated mainly by the rat. Trichinae are minute 



» Treadwell, A. L., The New International Year Book, 1910, p. 622. 

 2 LanU, David E., U. S. Dept. Agri., Biol. Surv. Bull. 33, 1909, p. 31. 



