66 POPULAR SCIENCE MONTHLY. 



the point of inoculation is inflamed and infiltrated with a bloody, 

 gelatinous exudate. The spleen is enlarged and sometimes the 

 lymphatic glands are swollen. The bacillus is found in the blood 

 and in all the organs. 



Mice and guinea pigs fed with pure cultures or with tissues 

 containing the germs die with the symptoms mentioned above. 

 Kitasato found the bacilli in a dead mouse from a plague- stricken 

 house. He also inoculated animals with dust gathered from such 

 houses, and one of these died with symptoms of the plague, and 

 the bacillus was found in its body. In certain parts of Asia 

 the disease is, according to Cantline, known as " rat plague," thus 

 indicating an extensive infection of these animals. 



Cantline makes the following statement concerning the sus- 

 ceptibility of rats to the disease : " On all hands rats are reported 

 to behave peculiarly and with a wonderful constancy. Before, or 

 it may be during an epidemic of plague, or before the individuals 

 in any particular house in an infected locality are stricken, the 

 rats leave their haunts and seek the interior of the house. They 

 become careless of the presence of man, and run about in a dazed 

 way with a peculiar limping jerk or spasm of their hind legs. 

 They are frequently found on the bedroom floor or on the tables, 

 but not infrequently their death is known by the putrefactive 

 odor of their decomposition arising from beneath the flooring. 

 So pertinent has this rat affection become, that during the epi- 

 demic in Macao in 1895 the Chinese and Portuguese left their 

 houses when the diseased rats invaded their premises. The cause 

 of the rats' behavior is undoubtedly disease, and the symptoms 

 tally wonderfully with plague symptoms of man. Dr. Rennie 

 examined them carefully in Canton, and noted the following post- 

 mortem appearances : (1) The stomach was distended and filled 

 with particles of food, sand, and indigestible substances, and the 

 mucous membrane was red and inflamed toward the pyloric end ; 

 (2) the liver was much enlarged and congested, and contained 

 ova of taenia and distoma ; (3) there was congestion at the base 

 of the lung present in about forty per cent ; and (4) glandular 

 enlargement was present in thirty per cent of those examined. 

 There is no doubt now that the disease in the rat and man is 

 identical. The bacillus of plague has been met with in every 

 case of rat disease of this description when it has been searched 

 for. The infection of the rat is raised from being a mere popular 

 belief into one of scientific precision, and we must now accept the 

 rat, at any rate, as one animal liable to the plague. Whether the 

 rat is affected previously to, coincidently with, or subsequently to 

 man being attacked is open to question. Is the disease among rats 

 a forerunner of its outbreak in man, and, if so, are they a means 

 of infection ? These are, of course, two separate questions." 



