vii INFECTION OF ANIMALS WITH PLAGUE 157 



been in the main recorded. I know from a personal 

 communication made to me by Professor Haffkine, that at 

 the Bombay Plague Laboratory attempts at producing 

 plague in rats by feeding have been uniformly un- 

 successful. 



I myself have to record a considerable number of 

 failures of the same kind. Guinea-pigs, rats, and mice 

 were repeatedly fed by me with milk culture and with 

 broth culture of B. pestis, as also with fresh organs (bubo, 

 spleen, liver, lung) of animals dead of typical plague : 

 but without result — the animals remained unaffected. 

 After a fortnight or so they were subjected to inoculation 

 with active B. pestis in an abrasion of the skin, in a 

 puncture of the oral mucous membrane, or by rubbing the 

 material well into puncture of the skin of the nostrils ; 

 and in all cases acute plague was the result. Only once 

 out of twenty experiments on sewer rats have I had 

 positive result by feeding. This rat had been fed (at the 

 same time as others) with plague organs of a rat dead of 

 inoculated plague ; and it too died of plague. The 

 intestine showed general congestion, and the mesenteric 

 glands were enlarged and much congested. But I did not 

 consider this a proof that the animal had become infected 

 by way of the intestine, because such a condition occurs 

 also not unfrequently after subcutaneous or cutaneous 

 inoculation ; and, further, because in the above rat the 

 lungs and bronchial glands were in the same condition as 

 the intestine and mesenteric glands. Be this, however, as 

 it may, it occurred to me that the probable reason why 

 simple feeding with plague organs or with active culture 

 of B. pestis is rarely followed by infection is that the 

 B. pestis is commonly destroyed by the secretion of the 



