4 QUATERCENTENARY STUDIES IN PATHOLOGY 



responsible for the existence of epidemic plague. Going into the 

 question more thoroughly, however, it is difficult to gauge exactly the 

 premises upon which such a conclusion has been drawn. We have to 

 consider whether rats are the only disseminators of plague — in fact, do 

 they disseminate plague epidemics at all ? — or, granting that they are re- 

 sponsible for the occurrence of such — are they solely responsible, or simply 

 partners in the wholesale serving up of the infection to the human species ? 



Plague in rats is by no means a recent discovery. Great 

 mortality in rats was noted by the ancients during outbreaks of plague. 

 Classical, mediaeval, and modern literature furnishes us with many 

 interesting details in regard to the susceptibility of various animals to 

 plague infection. The general lay opinion in regard to the matter was, 

 that during plague epidemics an increased mortality was observed 

 amongst animals in the infected district, and that such a death-rate was 

 noticeable especially amongst rats. 



It would be difficult to determine who propounded the rat theory of 

 plague epidemics. The prominence given to epizootic plague, during 

 recent years, has arisen out of better acquaintance with the bacteriological 

 and epidemiological aspects of the disease. 



In the year looo, Avicenna noted the presence of a high rat mortality 

 during plague epidemics. He says : — " Et de eis, quae significant illud, 

 est, ut videas mures, et animalia, quae habitant sub terra, fugere ad 

 superficiem terrae, et pari sedar,* id est commoveri hinc inde sicut 

 animalia ebria." 



Again Nicephorus Gregoras, in 1348, and Orraeus, in 1771, in their 

 Treatises on Medicine, look suspiciously upon rats as having some 

 relation to outbreaks of epidemic plague. 



Simpson, in his recent treatise on plague, and in his Report on 

 Plague in China and Hong-Kong, has given us an excellent resume of 

 the beliefs held by the Chinese in regard to the prevalence of the disease 

 in animals such as rats. It is evident that the opinion is widely diffused 

 amongst the Chinese that there exists some relation betw^een the epizootic 

 and the epidemic. In their writings, the Chinese make frequent mention 



* Pari sedar — an Arabic expression, the interpretation of which has given rise to some 

 difference of opinion. In Avicenna arabum medicorum principis. Liber quartus canonis, 

 ex Gerardi Cremonensis versione, et Andrea; Alpagi Bellunensis castigatione (Venetiis, mdxcv.), 

 torn. XL, tract. IV., cap. 3, p. 69, pari sedar is translated not as above but as "exire 

 manifeste." — Ed. 



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