vii INFECTION OF ANIMALS WITH PLAGUE 181 



must have arisen ample opportunity for B. pestis to pass 

 into and out from the large intestine with the alvine 

 evacuations of the infected animal. 



It is not possible to deny that similar conditions might 

 occur in respect of human beings ; that food-stuffs having 

 become polluted with, say, excreta of plague rats preserved 

 in a semi-dried or dried condition, might cause plague in 

 persons ingesting them, the point of infection in such 

 case being the intestine itself. 



Simpson's contention (Report on Plague in Hong- 

 Kong) that the septicemic form of plague in man (in 

 which the whole blood system and all organs contain 

 abundance of B. pestis) may be caused by infection of 

 man's intestine by means of food, was based on experi- 

 ments in which wild rats were fed with fresh plague 

 organs ; these rats, or some of them, having died, plague 

 was considered to have been induced in them by way of 

 the intestine. This inference seems to me, however, not 

 justified, or at least not proven, and for two reasons : — 



(1) The fact that the rats in question died, as is said 

 by Simpson, from the septicemic form of plague does not 

 afford presumption that they were infected by ingestion ; 

 the septicemic form of plague being that under which 

 both rats and mice and also guinea-pigs commonly die 

 after inoculation. 



(2) No indication is given by Simpson of any such 

 conspicuous and definite local infection (hemorrhage) in 

 the ileum and in Peyer's glands as that described by me 

 as resulting in those of my feeding experiments which 

 proved positive. 



The general congestion of the small intestine mentioned 

 by him (in addition to sanguineous mucus in the intestinal 



