lO 



QUATERCENTENARY STUDIES IN PATHOLOGY 



I. — The History of the Course and Relations of Epizootic and 



Epidemic Plague. 



{a) During the year igo2. 



The examination of rats was commenced in April. Previous to this 

 date it was impossible to say more than that casual examinations showed 

 rat plague to be existent. The extent and fluctuations of the epizootic, 

 however, were not accurately determined until my series of investigations 

 commenced. 



II o N a K o N a - 1 1) o sa . 



X.i^m. 



: uji ?.■( 4 111 



L 



III f^ 



Hiiniftn Plnjni* 



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r 



■1.1 



a^t4 



Chart I. 



IL' l.M iC, •> u. 16 23 30 7 U -n 2S 4 1 I IS L'i L' a 1« i3 30 



On examination of Chart I. for the year 1902, certain general 

 features are at once evident. The initial rise in rat plague is a 

 rapid one. It commences with 2, 4 or 6 cases per week. This number 

 is doubled or tripled during the succeeding weeks, and, with gradually 

 increasing amounts and fluctuations, the maximum of the epizootic is 



(224) 



