THE RAT THEORY OF PLAGUE EPIDEMICS 



19 



and oscillating curve. This curve is more regular in its course than 

 during the epidemic periods. 



From these curves, therefore, we find that rat plague is present 

 throughout the whole year in mild epizootic form. As a result of this, 

 sporadic cases of human plague appear from time to time. Epidemic 

 plague, on the other hand, is prevalent only during the acute exacer- 

 bations of epizootic plague. 



iioNaKONa-1002-00. 



(fi^. 



ru 



Lr 



^ 



,.j,„.._ Hum.. 1H.S'- 

 Rnl fin..... 



8 l.=.22?0 S 151920 •> D lfi2S30 7 14 21 1% \ 11 IS 2i 2 '.) IG 23 30 7 H21 2S •( II iSJ.i 4 11 Ig !,i I St522J3 C 132(127 .I 10 1724 



July, ■ August. . September. . October. .November.. December. . January. . February. March April. . May . June. 



1002., 1000. 



Chart VI. 



Another point of importance in regard to these two charts is the 

 following: — A comparison of the epizootic during i902-'o3 with that 

 during i903-'o4 shows us that the former was much more severe. 

 Secondly, the amount of rat plague at the end of 1902 was in excess ; 



(233) 



