148 ORIENTAL PLAGUE chap. 



to me to have a basis of direct experiment as regards the 

 species of rat and flea in question. 



Plague has been experimentally proved (see previous 

 chapters) to be transmissible in a number of ways, which 

 under natural conditions must needs frequently find their 

 counterpart. Thus, no one doubts that just as in the 

 laboratory cutaneous inoculation of the B. pestis is an 

 infallible means of producing plague in the rat, so also 

 under natural conditions an abrasion of the skin of this 

 animal may serve to give entrance to B. pestis. Similarly, 

 numerous cases of plague in human beings who, having 

 some broken skin on the hand, have handled plague 

 materials and developed axillary plague buboes on the 

 injured side, as also others who in a similar fashion have 

 contracted femoral plague bubo of one side owing to a 

 cutaneous injury on the foot of that side, are in no want 

 of explanation. Again, rats in their wild state are rarely 

 without some objective sign of their fighting habits — 

 wounds on tail or snout, for instance. Application of 

 B. pestis, present in infected food, filth, or other sub- 

 stances, to such wounds on tail or snout would, no doubt, 

 often result in plague of the animal thus, as it were, 

 inoculated. Further, no one doubts that the expectoration 

 of a case of pneumonic plague is charged with B. pestis, 

 or that such expectoration is highly infectious if it finds 

 entrance into a healthy person, as, for instance, along 

 with microscopic droplets of mucus coughed out into 

 the atmosphere by the affected patient. In a word, no 

 one doubts that so long as the B. pestis is present and 

 virulent in quality, its direct access to the tissues of a 

 susceptible human being or of a rat could, and often 

 would, cause the disease. Obviously, therefore, it is 



