88 



ORIENTAL PLAGUE 



CHAP. 



In support of the first of these criticisms it might be pointed out 

 that the proportion of vessels alleged to have had plague among 

 rats is larger in 1901 than in any previous year, due, it may be 

 alleged, to more careful search for suspicious sickness among these 

 rodents. It is difficult to appreciate the just value of this criticism 

 by reason of there being in many instances entire absence in the 

 accounts given, of any statement as to whether or not there had 

 been sickness among rats. In the 86 vessels (out of a total of 95) 

 on which plague appeared in man or in both man and rats, the pro- 

 portion in which definite statement is recorded as to the ' health ' of 

 rats on board appears from the following table : — 



There is nothing in the figures for the last three years of the 

 period 1898-1901 which appears to justify belief that increasing 

 watchfulness had led to detection of rat-sickness in an increasing 

 proportion of vessels on which there was human plague ; the figures 

 for 1898, however, are more open to doubt. On the whole, it seems 

 reasonable to assume that, in most cases, no statement as to the 

 health of rats implies that no sickness had been observed among 

 them. This, however, does not exclude the possibility, already re- 

 ferred to, of plague-sickness having been present among rats in a 

 form not readily recognisable. It is therefore possible that there 

 may have been instances among the 58 vessels where only human 

 plague was recognised, in which rats also were affected. 



In regard of the second criticism, that the disease observed 

 among rats may not have been plague in all instances, it is to be 

 noted that in the 28 ships in which both man and rats were 

 affected, positive bacteriological evidence as to its nature in these 

 rodents is recorded in seven instances only. As regards the 9 

 vessels in which the disease affected rats alone, there is positive 



