CHAPTEK V 



PLAGUE IN THE RAT 



In the 33rd Annual Keport of the Medical Officer of 

 the Local Government Board (1903-1904), Dr. Theodore 

 Thomson fully considered (pp. 317-329) the question of 

 the relation of plague in the rat to plague in man. He 

 has carefully on the basis of official data collected the 

 facts bearing on (1) the danger of transmission of in- 

 fection from shore to ship by plague-infected rats, (2) 

 the danger of transmission of infection from plague- 

 infected rats to man on board ship, and (3) the danger 

 of transmission of infection from ship to shore by plague- 

 infected rats. 



Dr. Thomson arrives (p. 320) at the same conclusions 

 which I have expressed in the Medical Officer's Report for 

 1902-1903, viz. : that in considering mortality among rats 

 on board ship, it is not necessary that this should be due 

 to plague, " but may be caused by other maladies in no 

 way related to that disease." " And we further know 

 that one of these maladies is characterised by the 

 presence in the rat of a micro-organism that cannot be 

 clearly differentiated from that of plague by micro- 

 scopic examination alone, but must have culture and 

 experiment." " So that it is open to serious doubt 



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