240 APPLIED BACTERIOLOGY 



The bacillus is also found in the blood and in the 

 enlarged spleen. Thus plague is a polyadenitis, the 

 glands being the starting-point of a septicsemia. The 

 micro-organism is found almost always in organs where 

 hemorrhages have taken place. 



Until the outbreak occurred in Hong Kong in 1894 but 

 very little was known of this disease, though it seems to 

 have existed in China and India from time immemorial, 

 breaking out periodically in the crowded cities. It appears 

 to be essentially a fiilth disease, and its existence can there- 

 fore hardly be wondered at when one considers the terribly, 

 insanitary condition of many Asiatic cities. The general 

 symptoms closely resemble those of the fatal epidemic 

 which visited Old London in the year 1665. 



Pathogenesis. — The disease may be regarded as of a 

 specific, acute, and infectious nature, characterised by a 

 severe general febrile condition, accompanied by inflamma- 

 tory swellings of the internal and external lymphatic glands 

 and of the spleen, by changes in the liver and kidneys, and 

 by inflammatory changes in the cerebral membranes. 



Three types of the disease are now recognised — namely, 

 the bubonic, the septicsemic, and the pneumonic. 



The period of incubation appears to be usually from 

 three to six days, but, according to Lowson, may extend 

 to nine days. The bacillus probably has access to the 

 body through wounds in the skin, or through the mucous 

 membrane of the alimentary tract. As all the poorer 

 classes of natives wear no footgear, it will be easy to see 

 how the disease might be propagated through scratches 

 or wounds of the foot, and also in other parts of the body 

 in the same manner. 



The thermal death-point of the organism appears to be 

 between 58° C. and 60° C. Light and partial desiccation 

 does not have much efifect upon cultures, but complete 



