154 OMENTAL PLAGUE chap. 



abundant opportunity of rat infecting rat can occur also 

 under natural conditions ; so that the transmission of 

 plague by fleas from the affected to the healthy rat would 

 at best but represent but one among many ways, one 

 moreover that would require more conditions for fulfil- 

 ment than many others. The chances, for instance, that 

 the bowel discharges, the kidney secretions, or the secre- 

 tions of the diseased lung of a plague rat would find 

 contact with an abrasion of the skin of the body, or even 

 with the skin and mucous membrane of nose and mouth 

 of healthy rats, are obviously greater than that a flea from 

 an infected rat retaining B. pestis after biting the plague 

 rat would settle on a fresh rat and communicate the 

 disease to it by its bite. I do not mean to doubt this 

 latter possibility — in fact, as I have already said, I con- 

 sider this theoretically quite possible. All I would urge 

 is : that the chances that it actually occurs, and, as some 

 would have it, frequently occurs, are far fewer than those 

 other chances mentioned above, viz. those that might 

 almost be called ever present during prevalence of plague 

 among rats. Dr. Tideswell's positive experiment appears 

 to me not cogent as to the transmission of plague from 

 rat to rat by the bite of the flea, and, so far, numerous 

 observations as to the presence of the true B. pestis in 

 fleas taken from rats affected with plague (including the 

 later experiments by Simmonds) have yielded negative 

 results (see the Eeport of the Bombay Plague Laboratory 

 for 1902). 



Hankin {Journal of Hygiene, vol. v. No. 1) describes 

 a single observation as to a flea which contained in its 

 stomach B. pestis, as shown by microscopic examination 

 and by culture. This, however, proves no more than that 



