THE RAT TttEORV OF t>LAGUE EPIDEMICS ^ 



that during, or immediately preceding, plague epidemics, severe outbreaks 

 of disease occur amongst their cattle, their fowls, and their house vermin. 



Reports such as these are extremely interesting to investigators of 

 the present day, who are endeavouring as far as possible to bring rats into 

 close relationship with the occurrence of plague amongst human beings. 



Within the past decade, much evidence of a more weighty character 

 has been brought forward in support of the rat theory of plague. The 

 experience gained by the outbreaks of plague in the seaports of Oporto, 

 Alexandria, Sydney, Kobe, London, etc., goes far to establish some 

 connection between rat and human plague. In these ports, as well as in 

 others, the disease clung fast to the harbour. The neighbouring cities 

 and villages were not, or only slightly, affected by the disease. 



Again, in the grossly overcrowded and filthy cities of the Orient, the 

 introduction of human plague has scarcely ever been followed by the 

 establishment of an actual endemic plague focus. In such cities or 

 ports, in which plague broke out epidemically, these epidemics would 

 not appear to depend on the arrival of plague-infected human beings, 

 but upon the introduction of plague-infected rats. 



In different plague epidemics, grain stores, in which rats preferably 

 lodge, have frequently become the central points of the outbreak. For 

 example, in Bombay, plague broke out first among the Banniahs 

 (German Plague Commission), and in Oporto the food stores appeared 

 to be the centres from which the epidemic spread. (Kossel and Frosch.) 



Of great importance are rats on board ship. Plague-infected rats 

 may be present on board ships, without the occurrence of human plague. 

 Further, plague rats, or the bodies of plague rats, on board ship, are 

 probably of greater importance than a plague-infected man. The 

 possibility of the infection of merchandise through plague-infected ship 

 rats is of great moment, and cases of such have been reported during 

 the past few years. According to Kossel and Nocht, merchant ships 

 have frequently arrived in Hamburg from plague-infected ports. No 

 cases of plague in man have occurred on board, but, on discharging the 

 cargo, numerous dead rats were found, many of which were plague- 

 infected. Similar instances have been found recently in Bristol, London 

 and Hong-Kong. In such cases, therefore, it is obvious that all 

 precautions must be exercised to prevent contact of the healthy rats on 

 shore with those on board ship or with the infected merchandise. 



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